AT80C51RD2-3CSCM

AT80C51RD2_08 ATMEL | Alldatasheet

Document overview

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Technical content

Features

• 80C52 Compatible – Four 8-bit I/O Ports – Three 16-bit Timer/Counters – 256 Bytes Scratch Pad RAM – 8 Interrupt Sources with 4 Priority Levels – Dual Data Pointer
• Variable Length MOVX for Slow RAM/Peripherals
• High-speed Architecture – 10 to 40 MHz in Standard Mode
• 16K/32K Bytes On-Chip ROM Program
• T80C51RD2 ROMless Versions
• On-Chip 1024 bytes Expanded RAM (XRAM) – Software Selectable Size (0, 256, 512, 768, 1024 b ytes) – 256 Bytes Selected at Reset for AT87C51RB2/RC2 Com patibility
• Keyboard Interrupt Interface on Port P1
• 8-bit Clock Prescaler
• 64K Program and Data Memory Spaces
• Improved X2 Mode with Independant Selection for CPU and Each Peripheral
• Programmable Counter Array 5 Channels with: – High-speed Output – Compare/Capture – Pulse Width Modulator – Watchdog Timer Capabilities
• Asynchronous Port Reset
• Full Duplex Enhanced UART
• Dedicated Baud Rate Generator for UART
• Low EMI (Inhibit ALE)
• Hardware Watchdog Timer (One-time Enabled with Reset-out)
• Power Control Modes – Idle Mode – Power-down Mode – Power-off Flag
• Power Supply: 2.7V to 5.5V or 2.7V to 3.6V
• Temperature Ranges: Commercial (0 to +70 °C) and Industrial (-40 °C to +85 °C)
• Packages: PDIL40, PLCC44, VQFP44 80C51 High Performance ROM 8-bit Microcontroller AT80C51RD2 AT83C51RB2 AT83C51RC2

trollers. They contain a 0K, 16K or 32K bytes ROM memory block for program. source 4-level interrupt controller and three timer/counters. multiprocessor communication (EUART) and a speed improvement mechanism (X2 mode). saved and all other functions are inoperative. Table 1. Memory Size

1. Alternate function of Port 3

4113C–8051–01/08 AT8xc51Rx2 3. Pin Configurations 3.1 P1.7CEX4 P1.4/CEX1 RST P3.0/RxD P3.1/TxD P1.3CEX0 P1.5/CEX2 P1.6/CEX3 P3.2/INT0 P3.3/INT1 P3.4/T0 P3.5/T1 P3.6/WR P3.7/RD XTAL2 XTAL1 VSS P2.0/AD8 P2.1/AD9 P2.2/AD10 P2.3/AD11 P2.4/AD12 P0.4/AD4 P0.6/AD6 P0.5/AD5 P0.7/AD7 ALE/PROG PSEN EA P2.7/AD15 P2.5/AD13 P2.6/AD14 P1.0/T2 P1.2/ECI P1.1/T2EX VCC P0.0/AD0 P0.1/AD1 P0.2/AD2 P0.3/AD3 PDIL40 43 42 41 40 39 44 38 37 36 35 34 P1.4/CEX1 P1.0/T2 P1.1/T2EX P1.3/CEX0 P1.2/ECI NIC* VCC P0.0/AD0 P0.2/AD2 P0.3/AD3 P0.1/AD1 P0.4/AD4 P0.6/AD6 P0.5/AD5 P0.7/AD7 ALE/PROG PSEN EA NIC* P2.7/A15 P2.5/A13 P2.6/A14 P1.5/CEX2 P1.6/CEX3 P1.7/CEX4 RST P3.0/RxD NIC* P3.1/TxD P3.2/INT0 P3.3/INT1 P3.4/T0 P3.5/T1 P3.6/WR P3.7/RD XTAL2 XTAL1 VSS P2.0/A8 P2.1/A9 P2.2/A10 P2.3/A11 P2.4/A12 NIC* 12 13 17 16 15 14 20 19 18 21 22 VQFP44 1.4 18 19 23 22 21 20 26 25 24 27 28 5 4 3 2 1 6 44 43 42 41 40 P1.4/CEX1 P1.0/T2 P1.1/T2EX P1.3/CEX0 P1.2/ECI NIC* VCC P0.0/AD0 P0.2/AD2 P0.1/AD1 P0.4/AD4 P0.6/AD6 P0.5/AD5 P0.7/AD7 ALE/PROG PSEN EA NIC* P2.7/A15 P2.5/A13 P2.6/A14 P3.6/WR P3.7/RD XTAL2 XTAL1 VSS P2.0/A8 P2.1/A9 P2.2/A10 P2.3/A11 P2.4/A12 P1.5/CEX2 P1.6/CEX3 P1.7/CEx4 RST P3.0/RxD NIC* P3.1/TxD P3.2/INT0 P3.3/INT1 P3.4/T0 P3.5/T1 P0.3/AD3 NIC* PLCC44 *NIC: No Internal Connection

4113C–8051–01/08 AT8xc51Rx2 Table 3-1. Pin Description Mnemonic Pin Number Type Name and Function DIL PLCC44 VQFP44 1.4 VSS 20 22 16 I Ground: 0V reference VCC 40 44 38 I Power Supply: This is the power supply voltage for normal, idle and power-down operation P0.0 - P0.7 39 - 32 43 - 36 37 - 30 I/O Port 0 : Port 0 is an open-drain, bi-directional I/O port. Port 0 pins that have 1s written to them float and can be used as high imped ance inputs. Port 0 must be polarized to V CC or V SS in order to prevent any parasitic current consumpt ion. Port 0 is also the multiplexed low-order address and data bus during access to external program and data memory. In this application, it us es strong internal pull-up when emitting 1s. Port 0 also inputs the code bytes duri ng EPROM programming. External pull-ups are required during program verif ication during which P0 outputs the code bytes. P1.0 - P1.7 1 - 8 2 - 9 40 - 44 1 - 3 I/O Port 1: Port 1 is an 8-bit bi-directional I/O port with in ternal pull-ups. Port 1 pins that have 1s written to them are pulled high by the internal pull-ups and can be used as inputs. As inputs, Port 1 pins that are ext ernally pulled low will source current because of the internal pull-ups. Port 1 also receives the low-order address byte during memory programming and verification. Alternate functions for T89C51RB2/RC2 Port 1 includ e: 1 2 40 I/O P1.0 : Input/Output I/O T2 (P1.0): Timer/Counter 2 external count input/Clockout 2 3 41 I/O P1.1: Input/Output I T2EX: Timer/Counter 2 Reload/Capture/Direction Control 3 4 42 I/O P1.2: Input/Output I ECI: External Clock for the PCA 4 5 43 I/O P1.3: Input/Output I/O CEX0: Capture/Compare External I/O for PCA module 0 5 6 44 I/O P1.4: Input/Output I/O CEX1: Capture/Compare External I/O for PCA module 1 6 7 1 I/O P1.5: Input/Output I/O CEX2: Capture/Compare External I/O for PCA module 2 7 8 2 I/O P1.6: Input/Output I/O CEX3: Capture/Compare External I/O for PCA module 3 8 9 3 I/O P1.7: Input/Output: I/O CEX4: Capture/Compare External I/O for PCA module 4 XTAL1 19 21 15 I Crystal 1: Input to the inverting oscillator amplifier and inp ut to the internal clock generator circuits. XTAL2 18 20 14 O Crystal 2: Output from the inverting oscillator amplifier

4113C–8051–01/08 AT8xc51Rx2 P2.0 - P2.7 21 - 28 24 - 31 18 - 25 I/O Port 2 : Port 2 is an 8-bit bi-directional I/O port with i nternal pull-ups. Port 2 pins that have 1s written to them are pulled high by the internal pull-ups and can be used as inputs. As inputs, Port 2 pins that are ext ernally pulled low will source current because of the internal pull-ups. Port 2 em its the high-order address byte during fetches from external program memory and dur ing accesses to external data memory that use 16-bit addresses (MOVX @DPTR). In this application, it uses strong internal pull-ups emitting 1s. During accesses to external data memory that use 8-bit addresses (MOVX @Ri), Port 2 emits t he contents of the P2 SFR. Some Port 2 pins receive the high order address bit s during ROM reading and verification: P2.0 to P2.5 for 16 KB devices P2.0 to P2.6 for 32 KB devices P3.0 - P3.7 10 - 17 11, 13 - 19 7 - 13 I/O Port 3: Port 3 is an 8-bit bi-directional I/O port with in ternal pull-ups. Port 3 pins that have 1s written to them are pulled high by the internal pull-ups and can be used as inputs. As inputs, Port 3 pins that are ext ernally pulled low will source current because of the internal pull-ups. Port 3 al so serves the special features of the 80C51 family, as listed below. 10 11 5 I RXD (P3.0): Serial input port 11 13 7 O TXD (P3.1): Serial output port 12 14 8 I INT0 (P3.2): External interrupt 0 13 15 9 I INT1 (P3.3): External interrupt 1 14 16 10 I T0 (P3.4): Timer 0 external input 15 17 11 I T1 (P3.5): Timer 1 external input 16 18 12 O WR (P3.6): External data memory write strobe 17 19 13 O RD (P3.7): External data memory read strobe RST 9 10 4 I/O Reset: A high on this pin for two machine cycles while th e oscillator is running, resets the device. An internal diffused resistor to V SS permits a power-on reset using only an external capacitor to V CC . This pin is an output when the hardware watchdog forces a system reset. ALE/PROG 30 33 27 O (I) Address Latch Enable/Program Pulse: Output pulse for latching the low byte of the address during an access to external memory. In normal operation, ALE is emitted at a constant rate of 1/6 (1/3 in X2 mode) the oscillator frequency, and can be used for external timing or clocking. Note that one ALE pulse is skipped during each access to external data memory. This pin is al so the program pulse input (PROG ) during Flash programming. ALE can be disabled by setting SFR’s AUXR.0 bit. With this bit set, ALE will be inactive during internal fetches. PSEN 29 32 26 O Program Strobe Enable: The read strobe to external program memory. When executing code from the external program memory, PS EN is activated twice each machine cycle, except that two PSEN activations are skipped during each access to external data memory. PSEN is not activated during fetches from internal program memory. EA 31 35 29 I External Access Enable: EA must be externally held low to enable the device t o fetch code from external program memory locations 0 000H to 3FFFH (16K), 7FFFH (32K). If security level 1 is programmed, EA will be internally latched on Reset. Table 3-1. Pin Description (Continued) Mnemonic Pin Number Type Name and Function DIL PLCC44 VQFP44 1.4

4113C–8051–01/08 AT8xc51Rx2 4. SFR Mapping The Special Function Registers (SFRs) of the microcontroller fall into the following categories:

• C51 core registers: ACC, B, DPH, DPL, PSW, SP
• I/O port registers: P0, P1, P2, P3
• Timer registers: T2CON, T2MOD, TCON, TH0, TH1, TH2 , TMOD, TL0, TL1, TL2, RCAP2L, RCAP2H
• Serial I/O port registers: SADDR, SADEN, SBUF, SCO N
• PCA (Programmable Counter Array) registers: CCON, CCAPMx, CL, CH, CCAPxH, CCAPxL (x: 0 to 4)
• Power and clock control registers: PCON
• Hardware Watchdog Timer registers: WDTRST, WDTPRG
• Interrupt system registers: IE0, IPL0, IPH0, IE1, IPL1, IPH1
• Keyboard Interface registers: KBE, KBF, KBLS
• BRG (Baud Rate Generator) registers: BRL, BDRCON
• Clock Prescaler register: CKRL
• Others: AUXR, AUXR1, CKCON0, CKCON1

4113C–8051–01/08 AT8xc51Rx2 Table 3 shows all SFRs with their address and their reset value. Table 4-1. SFR Mapping Bit Addressable Non-bit Addressable F8h CH 0000 0000 CCAP0H XXXX XXXX CCAP1H XXXX XXXX CCAPL2H XXXX XXXX CCAPL3H XXXX XXXX CCAPL4H XXXX XXXX FFh F0h B 0000 0000 F7h E8h CL 0000 0000 CCAP0L XXXX XXXX CCAP1L XXXX XXXX CCAPL2L XXXX XXXX CCAPL3L XXXX XXXX CCAPL4L XXXX XXXX EFh E0h ACC 0000 0000 E7h D8h CCON 00X0 0000 CMOD 00XX X000 CCAPM0 X000 0000 CCAPM1 X000 0000 CCAPM2 X000 0000 CCAPM3 X000 0000 CCAPM4 X000 0000 DFh D0h PSW 0000 0000 D7h C8h T2CON 0000 0000 T2MOD XXXX XX00 RCAP2L 0000 0000 RCAP2H 0000 0000 TL2 0000 0000 TH2 0000 0000 CFh C0h C7h B8h IPL0 X000 000 SADEN 0000 0000 BFh B0h P3 1111 1111 IE1 XXXX XXX0b IPL1 XXXX XXX0b IPH1 XXXX XXX0b IPH0 X000 0000 B7h A8h IE0 0000 0000 SADDR 0000 0000 AFh A0h P2 1111 1111 AUXR1 XXXX XXX0 WDTRST XXXX XXXX WDTPRG XXXX X000 A7h 98h SCON 0000 0000 SBUF XXXX XXXX BRL 0000 0000 BDRCON XXX0 0000 KBLS 0000 0000 KBE 0000 0000 KBF 0000 0000 9Fh 90h P1 1111 1111 CKRL 1111 1111 97h 88h TCON 0000 0000 TMOD 0000 0000 TL0 0000 0000 TL1 0000 0000 TH0 0000 0000 TH1 0000 0000 AUXR XX0X 0000 CKCON0 0000 0000 8Fh 80h P0 1111 1111 SP 0000 0111 DPL 0000 0000 DPH 0000 0000 PCON 00X1 0000 87h Reserved

4113C–8051–01/08 AT8xc51Rx2 5. Oscillators

5.1 Overview

One oscillator is available for CPU:

• OSC used for high frequency (3 MHz to 40 MHz) In order to optimize the power consumption and the execution time needed for a specific task, an internal prescaler feature has been implemented between the selected oscillator and the CPU.

5.2 Registers

Table 5-1. Clock Reload Register Reset Value = 1111 1111b Not bit addressable

5.2.1 Prescaler Divider

A hardware RESET puts the prescaler divider in the following state:

• CKRL = FFh: F CLK CPU = F CLK PERIPH = F OSC /2 (Standard C51 feature) KS signal selects OSC: F CLK OUT = F OSC
• Any value between FFh down to 00h can be written by software into CKRL register in order to divide frequency of the selected oscillator: – CKRL = 00h: minimum frequency FCLK CPU = F CLK PERIPH = F OSC /1020 (Standard Mode) FCLK CPU = F CLK PERIPH = F OSC /510 (X2 Mode) – CKRL = FFh: maximum frequency FCLK CPU = F CLK PERIPH = F OSC /2 (Standard Mode) FCLK CPU = F CLK PERIPH = F OSC (X2 Mode) – F CLK CPU and F CLK PERIPH In X2 mode: In X1 mode: 7 6 5 4 3 2 1 0 - - - - - - - - Bit Number Bit Mnemonic Description 7:0 CKRL Clock Reload Register: Prescaler value FC P U F= C L K P E R I P H FO S C FC P U F= C L K P E R I P H FO S C A

4113C–8051–01/08 AT8xc51Rx2 6. Enhanced Features In comparison to the original 80C52, the microcontrollers implement the following new features:

• X2 option
• Dual Data Pointer
• Extended RAM
• Programmable Counter Array (PCA)
• Hardware Watchdog
• 4-level Interrupt Priority System
• Power-off Flag
• Power On Reset
• ONCE mode
• ALE disabling
• Some enhanced features are also located in the UAR T and the Timer 2

6.1 X2 Feature and OSC Clock Generation

The microcontroller core needs only 6 clock periods per machine cycle. This feature called ”X2” provides the following advantages:

• Divides frequency crystals by 2 (cheaper crystals) while keeping same CPU power.
• Saves power consumption while keeping same CPU pow er (oscillator power saving).
• Saves power consumption by dividing dynamically th e operating frequency by 2 in operating and idle modes.
• Increases CPU power by 2 while keeping same crysta l frequency. In order to keep the original C51 compatibility, a divider by 2 is inserted between the XTAL1 sig- nal and the main clock input of the core (phase gen erator). This divider may be disabled by software.

6.1.1 Description

The clock for the whole circuit and peripherals is first divided by two before being used by the CPU core and the peripherals. This allows any cyclic ratio to be accepted on XTAL 1 input. In X2 mode, as this divider is bypassed, the signals on XTAL1 must have a cyclic ratio between 40 to 60%. Figure 6-1 shows the clock generation block diagram. X2 bit i s validated on the rising edge of the XTAL1 ÷ 2 to avoid glitches when switching from X2 to standard mode. Figure 6-2 shows the switching mode waveforms. Figure 6-1. Clock Generation Diagram XTAL1 2 CKCON0 8-bit Prescaler FOSC FXTAL XTAL1:2 CKRL CLK Periph CLK CPU Idle

4113C–8051–01/08 AT8xc51Rx2 Figure 6-2. Mode Switching Waveforms The X2 bit in the CKCON0 register (see Table 6-1) al lows to switch from 12 clock periods per instruction to 6 clock periods and vice versa. At r eset, the speed is set according to X2 bit of Hardware Config Byte (HCB). By default, Standard mo de is activated. Setting the X2 bit acti- vates the X2 feature (X2 mode). The T0X2, T1X2, T2X2, UARTX2, PCAX2 and WDX2 bits i n the CKCON0 register ( Table 6-1 ) allow to switch from standard peripheral speed (12 clock periods per peripheral clock cycle) to fast peripheral speed (6 clock periods per peripher al clock cycle). These bits are active only in X2 mode. Table 6-1. CKCON0 Register CKCON0 - Clock Control Register (8Fh) XTAL1:2 CPU Block X2 Bit X2 Mode STD Mode STD Mode FOSC XTAL1 7 6 5 4 3 2 1 0 - WDX2 PCAX2 SIX2 T2X2 T1X2 T0X2 X2 Bit Number Bit Mnemonic Description 7 - Reserved Do not set this bit.

6 WDX2

Watchdog clock (This control bit is validated when the CPU clock X 2 is set; when X2 is low, this bit has no effect). Cleared to select 6 clock periods per peripheral cl ock cycle. Set to select 12 clock periods per peripheral clock cycle.

4113C–8051–01/08 AT8xc51Rx2 Reset Value = 0000 000’HCB.X2’b (see Hardware Config Byte) Not bit addressable

5 PCAX2

Programmable Counter Array clock (This control bit is validated when the CPU clock X2 is set; when X2 is low, this bit has n o effect). Cleared to select 6 clock periods per peripheral cl ock cycle. Set to select 12 clock periods per peripheral clock cycle.

4 SIX2

Enhanced UART clock (Mode 0 and 2) (This control bit is validated when the CPU clock X2 is set; when X2 is low, this bit has n o effect). Cleared to select 6 clock periods per peripheral cl ock cycle. Set to select 12 clock periods per peripheral clock cycle.

3 T2X2

Timer 2 clock (This control bit is validated when the CPU clock X2 is set; when X2 is low, this bit has no effect). Cleared to select 6 clock periods per peripheral cl ock cycle. Set to select 12 clock periods per peripheral clock cycle.

2 T1X2

Timer 1 clock (This control bit is validated when the CPU clock X2 is set; when X2 is low, this bit has no effect). Cleared to select 6 clock periods per peripheral cl ock cycle. Set to select 12 clock periods per peripheral clock cycle

1 T0X2

Timer 0 clock (This control bit is validated when the CPU clock X2 is set; when X2 is low, this bit has no effect). Cleared to select 6 clock periods per peripheral cl ock cycle. Set to select 12 clock periods per peripheral clock cycle 0 X2 CPU clock Cleared to select 12 clock periods per machine cycle (STD mode) for CPU and all the peripherals. Set to select 6clock periods per machine cycle (X2 mode) and to enable the individual peripherals "X2" bits. Programmed by hardware after Power-up regarding Har dware Config Byte (HCB). Bit Number Bit Mnemonic Description

4113C–8051–01/08 AT8xc51Rx2 7. Dual Data Pointer Register The additional data pointer can be used to speed up code execution and reduce code size. The dual DPTR structure is a way by which the chip will specify the address of an external data memory location. There are two 16-bit DPTR register s that address the external memory, and a single bit called DPS = AUXR1.0 (see Table 7-1) that allows the program code to switch between them (Refer to Figure 7-1). Figure 7-1. Use of Dual Pointer Table 7-1. AUXR1 Register AUXR1- Auxiliary Register 1(0A2h) Reset Value: XXXX XXXX0b Not bit addressable Note: 1. Bit 2 stuck at 0; this allows to use INC AUX R1 to toggle DPS without changing GF3. External Data Memory AUXR1(A2H) DPS DPH(83H) DPL(82H) DPTR0 DPTR1 7 6 5 4 3 2 1 0 - - - - GF3 0 - DPS Bit Number Bit Mnemonic Description 7 - Reserved The value read from this bit is indeterminate. Do n ot set this bit. 6 - Reserved The value read from this bit is indeterminate. Do n ot set this bit. 5 - Reserved 4 - Reserved The value read from this bit is indeterminate. Do n ot set this bit. 3 GF3 This bit is a general purpose user flag. 2 0 Always cleared (1) . 1 - Reserved The value read from this bit is indeterminate. Do n ot set this bit.

0 DPS

Cleared to select DPTR0. Set to select DPTR1.

4113C–8051–01/08 AT8xc51Rx2

7.1 Assembly Language

; Block move using dual data pointers ; Modifies DPTR0, DPTR1, A and PSW ; note: DPS exits opposite of entry state ; unless an extra INC AUXR1 is added 00A2 AUXR1 EQU 0A2H 0000 909000MOV DPTR,#SOURCE ; address of SOURCE 0003 05A2 INC AUXR1 ; switch data pointers 0005 90A000 MOV DPTR,#DEST ; address of DEST

0008 LOOP:

0008 05A2 INC AUXR1 ; switch data pointers 000A E0 MOVX A,@DPTR ; get a byte from SOURCE 000B A3 INC DPTR ; increment SOURCE address 000C 05A2 INC AUXR1 ; switch data pointers 000E F0 MOVX @DPTR,A ; write the byte to DEST 000F A3 INC DPTR ; increment DEST address 0010 70F6JNZ LOOP ; check for 0 terminator 0012 05A2 INC AUXR1 ; (optional) restore DPS INC is a short (2 bytes) and fast (12 clocks) way t o manipulate the DPS bit in the AUXR1 SFR. However, note that the INC instruction does not dir ectly force the DPS bit to a particular state, but simply toggles it. In simple routines, such as the block move example, only the fact that DPS is toggled in the proper sequence matters, not its actual value. In other words, the block move routine works the same whether DPS is '0' or '1' on entry. Observe that without the last instruc- tion (INC AUXR1), the routine will exit with DPS in the opposite state.

4113C–8051–01/08 AT8xc51Rx2 8. Expanded RAM (XRAM) The AT8xc51Rx2 devices provide additional Bytes of Random Access Memory (RAM) space for increased data parameter handling and high level language usage. The devices have expanded RAM in external data spac e; maximum size and location are described in Table 8-1. Table 8-1. Expanded RAM The AT8xc51Rx2 has internal data memory that is mapped into four separate segments. The four segments are: 1. The Lower 128 bytes of RAM (addresses 00h to 7Fh) are directly and indirectly addressable. 2. The Upper 128 bytes of RAM (addresses 80h to FFh) are indirectly addressable only. 3. The Special Function Registers (SFRs) (addresses 80h to FFh) are directly address- able only. 4. The expanded RAM bytes are indirectly accessed by MOVX instructions, and with the EXTRAM bit cleared in the AUXR register (see Table 8-1). The lower 128 bytes can be accessed by either direc t or indirect addressing. The Upper 128 bytes can be accessed by indirect addressing only. The Upper 128 bytes occupy the same address space as the SFR. That means they have the same address, but are physically sepa- rate from SFR space. Figure 8-1. Internal and External Data Memory Address When an instruction accesses an internal location a bove address 7Fh, the CPU knows whether the access is to the upper 128 bytes of data RAM or to SFR space by the addressing mode used in the instruction.

• Instructions that use direct addressing access SFR space. For example: MOV 0A0H, # data, accesses the SFR at location 0A0h (which is P2). XRAM size Address Start End T83C51RB2/RC2 T80C51RD2 1024 00h 3FFh XRAM Upper

128 Bytes

indirect accesses Direct Accesses Direct or Indirect Accesses 7Fh

4113C–8051–01/08 AT8xc51Rx2

• Instructions that use indirect addressing access t he Upper 128 bytes of data RAM. For example: MOV @R0, # data where R0 contains 0A0h, accesses the data byte at address 0A0h, rather than P2 (whose address is 0A0h).
• The XRAM bytes can be accessed by indirect address ing, with EXTRAM bit cleared and MOVX instructions. This part of memory which is physically located on-chip, logically occupies the first bytes of external data memory. The bits XRS0 and XRS1 are used to hide a part of the available XRAM as explained in Table 8-1. This can be useful if external peripherals are mapped at addresses already used by the internal XRAM.
• With EXTRAM = 0, the XRAM is indirectly addressed, using the MOVX instruction in combination with any of the registers R0, R1 of the selected bank or DPTR. An access to XRAM will not affect ports P0, P2, P3.6 (WR) and P3.7 (RD). For example, with EXTRAM = 0, MOVX @R0, # data where R0 contains 0A0H, accesses the XRAM at address 0A0H rather than external memory. An access to external data memory locations higher than the accessible size of the XRAM will be performed with the MOVX DPTR instructions in the same way as in the standard 80C51, with P0 and P2 as data/address busses, and P3.6 and P3.7 as write and read timing signals. Accesses to XRAM above 0FFH can only be done by the use of DPTR.
• With EXTRAM = 1 , MOVX @Ri and MOVX @DPTR will be similar to the standard 80C51. MOVX @ Ri will provide an eight-bit address multiplexed with data on Port 0 and any output port pins can be used to output higher order address bits. This is to provide the external paging capability. MOVX @DPTR will generate a sixteen-bit address. Port2 outputs the high- order eight address bits (the contents of DPH) while Port0 multiplexes the low-order eight address bits (DPL) with data. MOVX @ Ri and MOVX @DPTR will generate either read or write signals on P3.6 (WR ) and P3.7 (RD ). The stack pointer (SP) may be located anywhere in t he 256 bytes RAM (lower and upper RAM) internal data memory. The stack may not be located in the XRAM. The M0 bit allows to stretch the XRAM timings; if M 0 is set, the read and write pulses are extended from 6 to 30 clock periods. This is useful to access external slow peripherals. Table 8-2. AUXR Register AUXR - Auxiliary Register (8Eh) 7 6 5 4 3 2 1 0 - - M0 - XRS1 XRS0 EXTRAM AO Bit Number Bit Mnemonic Description 7 - Reserved The value read from this bit is indeterminate. Do n ot set this bit 6 - Reserved The value read from this bit is indeterminate. Do n ot set this bit 5 M0 Pulse length Cleared to stretch MOVX control: the RD and the WR pulse length is 6 clock periods (default). Set to stretch MOVX control: the RD and the WR pulse length is 30 clock periods. 4 - Reserved The value read from this bit is indeterminate. Do n ot set this bit

4113C–8051–01/08 AT8xc51Rx2 Reset Value = XX0X 00’HSB.XRAM’0b (see Table 8-1 ) Not bit addressable

3 XRS1 XRAM Size

0 0 256 bytes (default) 0 1 512 bytes 1 0 768 bytes 1 1 1024 bytes

2 XRS0

1 EXTRAM

Cleared to access internal XRAM using MOVX @ Ri/ @ DPTR. Set to access external memory. Programmed by hardware after Power-up regarding Har dware Security Byte (HSB), default setting, XRAM selected. 0 AO ALE Output bit Cleared, ALE is emitted at a constant rate of 1/6 the oscillator frequency (or 1/3 if X2 mode is used) (default). Set, ALE is active only if a MOVX or MOVC instruction is used. Bit Number Bit Mnemonic Description

4113C–8051–01/08 AT8xc51Rx2 9. Timer 2 The Timer 2 in the AT8xc51Rx2 is the standard C52 Timer 2. It is a 16-bit timer/counter: the count is maintain ed by two eight-bit timer registers, TH2 and TL2 are cascaded. It is controlled by T2CON (Table 9-1) and T2MOD (Table 9-2) registers. Timer 2 operation is similar to Timer 0 and Timer 1. C/T2 selects F OSC /12 (timer operation) or external pin T2 (counter operation) as the timer clock input. Setting TR2 allows TL2 to be incremented by the selected input. Timer 2 has 3 operating modes: capture, auto-reload and Baud Rate Generator. These modes are selected by the combination of RCLK, TCLK and CP/RL2 (T2CON). Refer to the Atmel 8-bit Microcontroller Hardware description for Capture and Baud Rate Gen- erator Modes. Timer 2 includes the following enhancements:

• Auto-reload mode with up or down counter
• Programmable clock-output

9.1 Auto-reload Mode

The auto-reload mode configures Timer 2 as a 16-bit timer or event counter with automatic reload. If DCEN bit in T2MOD is cleared, Timer 2 be haves as in 80C52 (refer to the Atmel 8-bit Microcontroller Hardware description). If DCEN bit is set, Timer 2 acts as an Up/down timer/counter as shown in Figure 9-1. In this mode the T2EX pin controls the direction of count. When T2EX is high, Timer 2 counts up. Timer overflow occurs at FFFFh which sets the TF2 flag and generates an interrupt request. The overflow al so causes the 16-bit value in RCAP2H and RCAP2L registers to be loaded into the timer registers TH2 and TL2. When T2EX is low, Timer 2 counts down. Timer underf low occurs when the count in the timer registers TH2 and TL2 equals the value stored in RC AP2H and RCAP2L registers. The under- flow sets TF2 flag and reloads FFFFh into the timer registers. The EXF2 bit toggles when Timer 2 overflows or unde rflows according to the direction of the count. EXF2 does not generate any interrupt. This bit can be used to provide 17-bit resolution.

4113C–8051–01/08 AT8xc51Rx2 Figure 9-1. Auto-Reload Mode Up/Down Counter (DCEN = 1)

9.2 Programmable Clock-Output

In the clock-out mode, Timer 2 operates as a 50% du ty-cycle, programmable clock generator (see Figure 9-2). The input clock increments TL2 at frequency F CLK PERIPH /2. The timer repeat- edly counts to overflow from a loaded value. At overflow, the contents of RCAP2H and RCAP2L registers are loaded into TH2 and TL2. In this mode , Timer 2 overflows do not generate inter- rupts. The formula gives the clock-out frequency as a function of the system oscillator frequency and the value in the RCAP2H and RCAP2L registers: For a 16 MHz system clock, Timer 2 has a programmable frequency range of 61 Hz CLK PERIPH /2 16) to 4 MHz (F CLK PERIPH /4). The generated clock signal is brought out to T 2 pin (P1.0). Timer 2 is programmed for the clock-out mode as follows:

• Set T2OE bit in T2MOD register.
• Clear C/T2 bit in T2CON register.
• Determine the 16-bit reload value from the formula and enter it in RCAP2H/RCAP2L registers.
• Enter a 16-bit initial value in timer registers TH 2/TL2. It can be the same as the reload value or a different one depending on the application.
• To start the timer, set TR2 run control bit in T2CON register. (DOWN COUNTING RELOAD VALUE) C/T2 TF2 TR2 EXF2 TH2 (8-bit) TL2 (8-bit) RCAP2H (8-bit) RCAP2L (8-bit) FFh (8-bit) FFh (8-bit) TOGGLE (UP COUNTING RELOAD VALUE) TIMER 2 INTERRUPT FCLK PERIPH 0 T2CON T2CON T2CON T2CON T2EX: if DCEN = 1, 1 = UP if DCEN = 1, 0 = DOWN if DCEN = 0, up counting Cl o c k O u t Fr e qu e nc y – FC L K P E R I P H

4113C–8051–01/08 AT8xc51Rx2 It is possible to use Timer 2 as a baud rate genera tor and a clock generator simultaneously. For this configuration, the baud rates and clock freque ncies are not independent since both func- tions use the values in the RCAP2H and RCAP2L registers. Figure 9-2. Clock-Out Mode C/T2 = 07 Table 9-1. T2CON Register T2CON - Timer 2 Control Register (C8h) 7 6 5 4 3 2 1 0 TF2 EXF2 RCLK TCLK EXEN2 TR2 C/T2# CP/RL2# EXF2 TR2 OVEFLOW T2EX TH2 (8-bit) TL2 (8-bit) TIMER 2 RCAP2H (8-bit) RCAP2L (8-bit) T2OE FCLK PERIPH T2CON T2CON T2CON T2MOD INTERRUPT Q D Toggle EXEN2

4113C–8051–01/08 AT8xc51Rx2 Reset Value = 0000 0000b Bit addressable Table 9-2. T2MOD Register T2MOD - Timer 2 Mode Control Register (C9h) Bit Number Bit Mnemonic Description

7 TF2

Must be cleared by software. Set by hardware on Timer 2 overflow, if RCLK = 0 an d TCLK = 0.

6 EXF2

Set when a capture or a reload is caused by a negative transition on T2EX pin if EXEN2 = 1. When set, causes the CPU to vector to Timer 2 interrupt routine when Timer 2 interrupt is enabled. Must be cleared by software. EXF2 doesn’t cause an interrupt in Up/down counter mode (DCEN = 1)

5 RCLK

Cleared to use timer 1 overflow as receive clock fo r serial port in mode 1 or 3. Set to use Timer 2 overflow as receive clock for se rial port in mode 1 or 3.

4 TCLK

Cleared to use timer 1 overflow as transmit clock f or serial port in mode 1 or 3. Set to use Timer 2 overflow as transmit clock for s erial port in mode 1 or 3.

3 EXEN2

Timer 2 External Enable bit Cleared to ignore events on T2EX pin for Timer 2 op eration. Set to cause a capture or reload when a negative transition on T2EX pin is detected, if Timer 2 is not used to clock the seria l port.

2 TR2

Cleared to turn off Timer 2. Set to turn on Timer 2.

1 C/T2#

Timer/Counter 2 select bit Cleared for timer operation (input from internal cl ock system: F CLK PERIPH ). Set for counter operation (input from T2 input pin, falling edge trigger). Must be 0 for clock out mode.

0 CP/RL2#

Timer 2 Capture/Reload bit If RCLK = 1 or TCLK = 1, CP/RL2# is ignored and timer is forced to auto-reload on Timer 2 overflow. Cleared to auto-reload on Timer 2 overflows or negative transitions on T2EX pin if EXEN2 = 1. Set to capture on negative transitions on T2EX pin if EXEN2 = 1. 7 6 5 4 3 2 1 0 - - - - - - T2OE DCEN

4113C–8051–01/08 AT8xc51Rx2 Reset Value = XXXX XX00b Not bit addressable Bit Number Bit Mnemonic Description 7 - Reserved The value read from this bit is indeterminate. Do n ot set this bit. 6 - Reserved The value read from this bit is indeterminate. Do n ot set this bit. 5 - Reserved The value read from this bit is indeterminate. Do n ot set this bit. 4 - Reserved The value read from this bit is indeterminate. Do n ot set this bit. 3 - Reserved The value read from this bit is indeterminate. Do n ot set this bit. 2 - Reserved The value read from this bit is indeterminate. Do n ot set this bit.

1 T2OE

Cleared to program P1.0/T2 as clock input or I/O po rt. Set to program P1.0/T2 as clock output.

0 DCEN

Cleared to disable Timer 2 as up/down counter. Set to enable Timer 2 as up/down counter.

4113C–8051–01/08 AT8xc51Rx2 10. Programmable Counter Array (PCA) The PCA provides more timing capabilities with less CPU intervention than the standard timer/counters. Its advantages include reduced soft ware overhead and improved accuracy. The PCA consists of a dedicated timer/counter which ser ves as the time base for an array of five compare/capture modules. Its clock input can be pro grammed to count any one of the following signals:

• Peripheral clock frequency (F CLK PERIPH ) ÷ 6
• Peripheral clock frequency (F CLK PERIPH ) ÷ 2
• Timer 0 overflow
• External input on ECI (P1.2) Each compare/capture modules can be programmed in a ny one of the following modes:
• Rising and/or falling edge capture
• Software timer
• High-speed output
• Pulse width modulator Module 4 can also be programmed as a Watchdog Timer (see Section "PCA Watchdog Timer", page 33). When the compare/capture modules are programmed in the capture mode, software timer, or high-speed output mode, an interrupt can be generat ed when the module executes its function. All five modules plus the PCA timer overflow share one interrupt vector. The PCA timer/counter and compare/capture modules s hare Port 1 for external I/O. These pins are listed below. If the port is not used for the PCA, it can still be used for standard I/O. The PCA timer is a common time base for all five mo dules (see Figure 10-1). The timer count source is determined from the CPS1 and CPS0 bits in the CMOD register (Table 10-1) and can be programmed to run at:
• 1/6 the peripheral clock frequency (F CLK PERIPH )
• 1/2 the peripheral clock frequency (F CLK PERIPH )
• The Timer 0 overflow
• The input on the ECI pin (P1.2) PCA Component External I/O Pin 16-bit Counter P1.2/ECI 16-bit Module 0 P1.3/CEX0 16-bit Module 1 P1.4/CEX1 16-bit Module 2 P1.5/CEX2 16-bit Module 3 P1.6/CEX3

4113C–8051–01/08 AT8xc51Rx2 Figure 10-1. PCA Timer/Counter Table 10-1. CMOD Register CMOD - PCA Counter Mode Register (D9h) CIDL CPS1 CPS0 ECF It CH CL 16-Bit Up/Down Counter To PCA Modules F CLK PERIPH /6 FCLK PERIPH /2 T0 OVF P1.2 Idle CMOD 0xD9 WDTE CF CR CCON 0xD8 CCF4 CCF3 CCF2 CCF1 CCF0 Overflow 7 6 5 4 3 2 1 0 CIDL WDTE - - - CPS1 CPS0 ECF

4113C–8051–01/08 AT8xc51Rx2 Reset Value = 00XX X000b Not bit addressable The CMOD register includes three additional bits as sociated with the PCA (see Figure 10-4 and Table 10-1).

• The CIDL bit which allows the PCA to stop during i dle mode.
• The WDTE bit which enables or disables the watchdo g function on module 4.
• The ECF bit which when set causes an interrupt and the PCA overflow flag CF (in the CCON SFR) to be set when the PCA timer overflows. The CCON register contains the run control bit for the PCA and the flags for the PCA timer (CF) and each module (see Table 10-2).
• Bit CR (CCON.6) must be set by software to run the PCA. The PCA is shut off by clearing this bit.
• Bit CF: The CF bit (CCON.7) is set when the PCA co unter overflows and an interrupt will be generated if the ECF bit in the CMOD register is set. The CF bit can only be cleared by software.
• Bits 0 through 4 are the flags for the modules (bit 0 for module 0, bit 1 for module 1, etc.) and are set by hardware when either a match or a capture occurs. These flags can only be cleared by software. Table 10-2. CCON Register Bit Number Bit Mnemonic Description

7 CIDL

Cleared to program the PCA Counter to continue func tioning during idle Mode. Set to program PCA to be gated off during idle.

6 WDTE

Cleared to disable Watchdog Timer function on PCA M odule 4. Set to enable Watchdog Timer function on PCA Module 4. 5 - Reserved The value read from this bit is indeterminate. Do n ot set this bit. 4 - Reserved The value read from this bit is indeterminate. Do n ot set this bit. 3 - Reserved The value read from this bit is indeterminate. Do n ot set this bit.

2 CPS1 PCA Count Pulse Select

CPS1CPS0 Selected PCA input 0 0 Internal clock f CLK PERIPH/6 0 1 Internal clock f CLK PERIPH/2 1 0 Timer 0 Overflow 1 1 External clock at ECI/P1.2 pin (max rate = f CLK PERIPH/4 )

1 CPS0

0 ECF

PCA Enable Counter Overflow Interrupt Cleared to disable CF bit in CCON to inhibit an int errupt. Set to enable CF bit in CCON to generate an interru pt.

4113C–8051–01/08 AT8xc51Rx2 CCON - PCA Counter Control Register (D8h) Reset Value = 000X 0000b Not bit addressable The watchdog timer function is implemented in module 4 (see Figure 10-4). The PCA interrupt system is shown in Figure 10-2. 7 6 5 4 3 2 1 0 CF CR - CCF4 CCF3 CCF2 CCF1 CCF0 Bit Number Bit Mnemonic Description 7 CF PCA Counter Overflow flag Set by hardware when the counter rolls over. CF fla gs an interrupt if bit ECF in CMOD is set. CF may be set by either hardware or so ftware but can only be cleared by software. 6 CR PCA Counter Run control bit Must be cleared by software to turn the PCA counter off. Set by software to turn the PCA counter on. 5 - Reserved The value read from this bit is indeterminate. Do n ot set this bit.

4 CCF4

PCA Module 4 interrupt flag Must be cleared by software. Set by hardware when a match or capture occurs.

3 CCF3

PCA Module 3 interrupt flag Must be cleared by software. Set by hardware when a match or capture occurs.

2 CCF2

PCA Module 2 interrupt flag Must be cleared by software. Set by hardware when a match or capture occurs.

1 CCF1

PCA Module 1 interrupt flag Must be cleared by software. Set by hardware when a match or capture occurs.

0 CCF0

PCA Module 0 interrupt flag Must be cleared by software. Set by hardware when a match or capture occurs.

4113C–8051–01/08 AT8xc51Rx2 Figure 10-2. PCA Interrupt System PCA Modules: each one of the five compare/capture modules has si x possible functions. It can perform:

• 16-bit Capture, positive-edge triggered
• 16-bit Capture, negative-edge triggered
• 16-bit Capture, both positive and negative-edge tr iggered
• 16-bit Software Timer
• 16-bit High-speed Output
• 8-bit Pulse Width Modulator In addition, module 4 can be used as a Watchdog Timer. Each module in the PCA has a special function regis ter associated with it. These registers are: CCAPM0 for module 0, CCAPM1 for module 1, etc. (see Table 10-3). The registers contain the bits that control the mode that each module will operate in.
• The ECCF bit (CCAPMn.0 where n = 0, 1, 2, 3, or 4 depending on the module) enables the CCF flag in the CCON SFR to generate an interrupt when a match or compare occurs in the associated module.
• PWM (CCAPMn.1) enables the pulse width modulation mode.
• The TOG bit (CCAPMn.2) when set causes the CEX out put associated with the module to toggle when there is a match between the PCA counter and the module's capture/compare register.
• The match bit MAT (CCAPMn.3) when set will cause the CCFn bit in the CCON register to be set when there is a match between the PCA counter and the module's capture/compare register.
• The next two bits CAPN (CCAPMn.4) and CAPP (CCAPMn .5) determine the edge that a capture input will be active on. The CAPN bit enables the negative edge, and the CAPP bit enables the positive edge. If both bits are set both edges will be enabled and a capture will occur for either transition.
• The last bit in the register ECOM (CCAPMn.6) when set enables the comparator function. CF CR CCON 0xD8 CCF4 CCF3 CCF2 CCF1 CCF0 Module 4 Module 3 Module 2 Module 1 Module 0 ECF PCA Timer/Counter ECCFn CCAPMn.0 CMOD.0 IE.6 IE.7 To Interrupt Priority Decoder EC EA

4113C–8051–01/08 AT8xc51Rx2 Table 10-3 shows the CCAPMn settings for the various PCA functions. Table 10-3. CCAPMn Registers (n = 0-4) CCAPM0 - PCA Module 0 Compare/Capture Control Regis ter (0DAh) CCAPM1 - PCA Module 1 Compare/Capture Control Regis ter (0DBh) CCAPM2 - PCA Module 2 Compare/Capture Control Regis ter (0DCh) CCAPM3 - PCA Module 3 Compare/Capture Control Regis ter (0DDh) CCAPM4 - PCA Module 4 Compare/Capture Control Regis ter (0DEh) Reset Value = X000 0000b Not bit addressable 7 6 5 4 3 2 1 0 - ECOMn CAPPn CAPNn MATn TOGn PWMn ECCFn Bit Number Bit Mnemonic Description 7 - Reserved The value read from this bit is indeterminate. Do n ot set this bit.

6 ECOMn

Cleared to disable the comparator function. Set to enable the comparator function.

5 CAPPn

Cleared to disable positive edge capture. Set to enable positive edge capture.

4 CAPNn

Cleared to disable negative edge capture. Set to enable negative edge capture.

3 MATn

When MATn = 1, a match of the PCA counter with this module's compare/capture register causes the CCFn bit in CCO N to be set, flagging an interrupt.

2 TOGn

When TOGn = 1, a match of the PCA counter with this module's compare/capture register causes the CEXn pin to tog gle.

1 PWMn

Pulse Width Modulation Mode Cleared to disable the CEXn pin to be used as a pul se width modulated output. Set to enable the CEXn pin to be used as a pulse wi dth modulated output. Cleared to disable compare/capture flag CCFn in the CCON register to generate an interrupt. Set to enable compare/capture flag CCFn in the CCON register to generate an interrupt.

4113C–8051–01/08 AT8xc51Rx2 Table 10-4. PCA Module Modes (CCAPMn Registers) There are two additional registers associated with each of the PCA modules. They are CCAPnH and CCAPnL and these are the registers that store t he 16-bit count when a capture occurs or a compare should occur. When a module is used in the PWM mode these registers are used to control the duty cycle of the output (see Table 10-5 and Table 10-6). Table 10-5. CCAPnH Registers (n = 0-4) CCAP0H - PCA Module 0 Compare/Capture Control Register High (0FAh) CCAP1H - PCA Module 1 Compare/Capture Control Register High (0FBh) CCAP2H - PCA Module 2 Compare/Capture Control Register High (0FCh) CCAP3H - PCA Module 3 Compare/Capture Control Register High (0FDh) CCAP4H - PCA Module 4 Compare/Capture Control Register High (0FEh) Reset Value = 0000 0000b Not bit addressable Table 10-6. CCAPnL Registers (n = 0-4) CCAP0L - PCA Module 0 Compare/Capture Control Regis ter Low (0EAh) CCAP1L - PCA Module 1 Compare/Capture Control Regis ter Low (0EBh) CCAP2L - PCA Module 2 Compare/Capture Control Regis ter Low (0ECh) CCAP3L - PCA Module 3 Compare/Capture Control Regis ter Low (0EDh) ECOMn CAPPn CAPNn MATn TOGn PWMm ECCFn Module Function 0 0 0 0 0 0 0 No Operation X 1 0 0 0 0 X 16-bit capture by a positive-edge trigger on CEXn X 0 1 0 0 0 X 16-bit capture by a negative trigger on CEXn X 1 1 0 0 0 X 16-bit capture by a transition on CEXn 1 0 0 1 0 0 X 16-bit Software Timer/Compare mode. 1 0 0 1 1 0 X 16-bit High-speed Output 1 0 0 0 0 1 0 8-bit PWM 1 0 0 1 X 0 X Watchdog Timer (module 4 only) 7 6 5 4 3 2 1 0 - - - - - - - - Bit Number Bit Mnemonic Description 7-0 - PCA Module n Compare/Capture Control CCAPnH Value

4113C–8051–01/08 AT8xc51Rx2 CCAP4L - PCA Module 4 Compare/Capture Control Regis ter Low (0EEh) Reset Value = 0000 0000b Not bit addressable Table 10-7. CH Register CH - PCA Counter Register High (0F9h) Reset Value = 0000 0000b Not bit addressable Table 10-8. CL Register CL - PCA Counter Register Low (0E9h) Reset Value = 0000 0000b Not bit addressable

10.1 PCA Capture Mode

To use one of the PCA modules in the capture mode e ither one or both of the CCAPM bits CAPN and CAPP for that module must be set. The external CEX input for the module (on port 1) is sampled for a transition. When a valid transitio n occurs the PCA hardware loads the value of the PCA counter registers (CH and CL) into the modu le's capture registers (CCAPnL and CCAPnH). If the CCFn bit for the module in the CCON SFR and the ECCFn bit in the CCAPMn SFR are set then an interrupt will be generated (see Figure 10-3). 7 6 5 4 3 2 1 0 - - - - - - - - Bit Number Bit Mnemonic Description 7-0 - PCA Module n Compare/Capture Control CCAPnL Value 7 6 5 4 3 2 1 0 - - - - - - - - Bit Number Bit Mnemonic Description 7-0 - PCA counter CH Value 7 6 5 4 3 2 1 0 - - - - - - - - Bit Number Bit Mnemonic Description 7-0 - PCA Counter CL Value

4113C–8051–01/08 AT8xc51Rx2 Figure 10-3. PCA Capture Mode 10.2 16-bit Software Timer/ Compare Mode The PCA modules can be used as software timers by s etting both the ECOM and MAT bits in the modules CCAPMn register. The PCA timer will be compared to the module's capture regis- ters and when a match occurs an interrupt will occu r if the CCFn (CCON SFR) and the ECCFn (CCAPMn SFR) bits for the module are both set (see Figure 10-4). CF CR CCON 0xD8 CH CL CCAPnH CCAPnL CCF4 CCF3 CCF2 CCF1 CCF0 PCA IT PCA Counter/Timer ECOMn CCAPMn, n= 0 to 4 0xDA to 0xDE CAPNn MATn TOGn PWMn ECCFn CAPPn Cex.n Capture

4113C–8051–01/08 AT8xc51Rx2 Figure 10-4. PCA Compare Mode and PCA Watchdog Timer Before enabling ECOM bit, CCAPnL and CCAPnH should be set with a non zero value, other- wise an unwanted match could happen. Writing to CCAPnH will set the ECOM bit. Once ECOM set, writing CCAPnL will clear ECOM so th at an unwanted match doesn’t occur while modifying the compare value. Writing to CCAPn H will set ECOM. For this reason, user software should write CCAPnL first, and then CCAPnH . Of course, the ECOM bit can still be controlled by accessing to CCAPMn register.

10.3 High-speed Output Mode

In this mode, the CEX output (on port 1) associated with the PCA module will toggle each time a match occurs between the PCA counter and the module 's capture registers. To activate this mode the TOG, MAT, and ECOM bits in the module's CC APMn SFR must be set (see Figure 10-5). A prior write must be done to CCAPnL and CCAPnH before writing the ECOMn bit. CH CL CCAPnH CCAPnL ECOMn CCAPMn, n = 0 to 4 0xDA to 0xDE CAPNn MATn TOGn PWMn ECCFn CAPPn 16 bit comparator Match CCON 0xD8 PCA IT Enable PCA counter/timer RESET * CIDL CPS1 CPS0 ECF CMOD 0xD9 WDTE Reset Write to CCAPnL Write to CCAPnH CF CCF2 CCF1 CCF0 CR CCF3 CCF4 1 0

4113C–8051–01/08 AT8xc51Rx2 Figure 10-5. PCA High-speed Output Mode Before enabling ECOM bit, CCAPnL and CCAPnH should be set with a non zero value, other- wise an unwanted match could occur. Once ECOM is set, writing CCAPnL will clear ECOM so that an unwanted match doesn’t occur while modifying the compare value. Writing to CCAPn H will set ECOM. For this reason, user software should write CCAPnL first, and then CCAPnH . Of course, the ECOM bit can still be controlled by accessing the CCAPMn register.

10.4 Pulse Width Modulator Mode

All of the PCA modules can be used as PWM outputs. Figure 10-6 shows the PWM function. The frequency of the output depends on the source f or the PCA timer. All of the modules will have the same frequency of output because they all share the PCA timer. The duty cycle of each module is independently variable using the module's capture register CCAPLn. When the value of the PCA CL SFR is less than the value in the mod ule's CCAPLn SFR the output will be low, when it is equal to or greater than the output will be high. When CL overflows from FF to 00, CCAPLn is reloaded with the value in CCAPHn. This a llows updating the PWM without glitches. The PWM and ECOM bits in the module's CCAPMn regist er must be set to enable the PWM mode. CH CL CCAPnH CCAPnL ECOMn CCAPMn, n = 0 to 4 0xDA to 0xDE CAPNn MATn TOGn PWMn ECCFn CAPPn 16 bit comparator Match CF CR CCON 0xD8 CCF4 CCF3 CCF2 CCF1 CCF0 PCA IT Enable CEXn PCA counter/timer Write to CCAPnH Reset Write to CCAPnL 1 0

4113C–8051–01/08 AT8xc51Rx2 Figure 10-6. PCA PWM Mode

10.5 PCA Watchdog Timer

An on-board watchdog timer is available with the PC A to improve the reliability of the system without increasing chip count. Watchdog timers are useful for systems that are susceptible to noise, power glitches, or electrostatic discharge. Module 4 is the only PCA module that can be programmed as a watchdog. However, this module can still be used for other modes if the watchdog is not needed. Figure 10-4 shows a diagram of how the watchdog works. The user pre-loads a 16-bit value in the compare registers. Just like the other compare modes, this 16-bit value is compared to the PCA timer value. If a match is allowed to occur, an internal reset will be generated. This will not cause the RST pin to be driven high. In order to hold off the reset, the user has three options: 1. Periodically change the compare value so it will never match the PCA timer. 2. Periodically change the PCA timer value so it wil l never match the compare values. 3. Disable the watchdog by clearing the WDTE bit bef ore a match occurs and then re- enable it. The first two options are more reliable because the watchdog timer is never disabled as in option #3. If the program counter ever goes astray, a matc h will eventually occur and cause an internal reset. The second option is also not recommended if other PCA modules are being used. Remember, the PCA timer is the time base for all mo dules; changing the time base for other modules would not be a good idea. Thus, in most applications the first solution is the best option. This watchdog timer won’t generate a reset out on the reset pin. CL CCAPnH CCAPnL ECOMn CCAPMn, n= 0 to 4 0xDA to 0xDE CAPNn MATn TOGn PWMn ECCFn CAPPn 8-Bit Comparator CEXn “0” “1” Enable PCA Counter/Timer Overflow

4113C–8051–01/08 AT8xc51Rx2 11. Serial I/O Port The serial I/O port in the AT8xc51Rx2 is compatible with the serial I/O port in the 80C52. It provides both synchronous and asynchronous communication modes. It operates as a Univer- sal Asynchronous Receiver and Transmitter (UART) in three full-duplex modes (Modes 1, 2 and 3). Asynchronous transmission and reception can occ ur simultaneously and at different baud rates Serial I/O port includes the following enhancements:

• Framing error detection
• Automatic address recognition

11.1 Framing Error Detection

Framing bit error detection is provided for the three asynchronous modes (modes 1, 2 and 3). To enable the framing bit error detection feature, set SMOD0 bit in PCON register (see Figure 11- 1). Figure 11-1. Framing Error Block diagram When this feature is enabled, the receiver checks e ach incoming data frame for a valid stop bit. An invalid stop bit may result from noise on the serial lines or from simultaneous transmission by two CPUs. If a valid stop bit is not found, the Framing Error bit (FE) in SCON register (see Table 11-4 ) bit is set. Software may examine FE bit after each reception to check for data errors. Once set, only soft- ware or a reset can clear FE bit. Subsequently, received frames with valid stop bits cannot clear FE bit. When FE feature is enabled, RI rises on sto p bit instead of the last data bit (see Figure 11-2 and Figure 11-3 ). Figure 11-2. UART Timings in Mode 1 RI TI RB8 TB8 RE N SM2 SM1 SM0/FE IDL PD GF0 GF1 PO F -SMOD0 SMOD1 To UA RT fra ming error co nt rol SM0 to UA RT mo de control (SMOD0 = 0 ) Se t FE bit if stop bit is 0 (framing error) (SMOD0 = 1) S CO N (9 8h ) PCON (87h) 1 Data byte RI SMOD0=X Stop bit Start bit RXD D7 D6 D5 D4 D3 D2 D1 D0 FE SMOD0=1

4113C–8051–01/08 AT8xc51Rx2 Figure 11-3. UART Timings in Modes 2 and 3

11.2 Automatic Address Recognition

The automatic address recognition feature is enable d when the multiprocessor communication feature is enabled (SM2 bit in SCON register is set). Implemented in hardware, automatic address recognit ion enhances the multiprocessor commu- nication feature by allowing the serial port to exa mine the address of each incoming command frame. Only when the serial port recognizes its own address, the receiver sets RI bit in SCON register to generate an interrupt. This ensures tha t the CPU is not interrupted by command frames addressed to other devices. If desired, you may enable the automatic address re cognition feature in mode 1. In this configu- ration, the stop bit takes the place of the ninth d ata bit. Bit RI is set only when the received command frame address matches the device’s address and is terminated by a valid stop bit. To support automatic address recognition, a device is identified by a given address and a broad- cast address. Note: The multiprocessor communication and automatic address recognition features cannot be enabled in mode 0 (i.e. setting SM2 bit in SCON register in mode 0 has no effect).

11.2.1 Given Address

Each device has an individual address that is speci fied in SADDR register; the SADEN register is a mask byte that contains don’t care bits (defin ed by zeros) to form the device’s given address. The don’t care bits provide the flexibilit y to address one or more slaves at a time. The following example illustrates how a given address is formed. To address a device by its individual address, the SADEN mask byte must be 1111 1111b . For example: SADDR0101 0110b SADEN 1111 1100b Given0101 01XXb The following is an example of how to use given addresses to address different slaves: Slave A:SADDR1111 0001b SADEN 1111 1010b Given1111 0X0Xb Slave B:SADDR1111 0011b SADEN 1111 1001b RI SMOD0 = 0 Data Byte Ninth Bit Stop Bit .Start Bit RXD D8 D7 D6 D5 D4 D3 D2 D1 D0 RI SMOD0 = 1 FE SMOD0 = 1

4113C–8051–01/08 AT8xc51Rx2 Given1111 0XX1b Slave C:SADDR1111 0010b SADEN 1111 1101b Given1111 00X1b The SADEN byte is selected so that each slave may be addressed separately. For slave A, bit 0 (the LSB) is a don’t-care bit; f or slaves B and C, bit 0 is a 1. To communicate with slave A only, the master must send an address where bit 0 is clear (e.g. 1111 0000b ). For slave A, bit 1 is a 1; for slaves B and C, bit 1 is a don’t care bit. To communicate with slaves B and C, but not slave A, the master must send an address with bits 0 and 1 both set (e.g. 1111 0011b ). To communicate with slaves A, B and C, the master m ust send an address with bit 0 set, bit 1 clear, and bit 2 clear (e.g. 1111 0001b ).

11.2.2 Broadcast Address

A broadcast address is formed from the logical OR o f the SADDR and SADEN registers with zeros defined as don’t-care bits, e.g.: SADDR0101 0110b SADEN1111 1100b Broadcast = SADDR OR SADEN1111 111Xb The use of don’t-care bits provides flexibility in defining the broadcast address, however in most applications, a broadcast address is FFh. The follo wing is an example of using broadcast addresses: Slave A:SADDR1111 0001b SADEN 1111 1010b Broadcast1111 1X11b, Slave B:SADDR1111 0011b SADEN 1111 1001b Broadcast1111 1X11B, Slave C:SADDR = 1111 0010b SADEN 1111 1101b Broadcast1111 1111b For slaves A and B, bit 2 is a don’t care bit; for slave C, bit 2 is set. To communicate with all of the slaves, the master must send an address FFh. To communicate with slaves A and B, but not slave C, the master can send and address FBh.

4113C–8051–01/08 AT8xc51Rx2

11.2.3 Reset Addresses

On reset, the SADDR and SADEN registers are initial ized to 00h, i.e. the given and broadcast addresses are XXXX XXXXb (all don’t-care bits). This ensures that the serial port will reply to any address, and so, that it is backwards compatible wi th the 80C51 microcontrollers that do not support automatic address recognition. Table 11-1. SADEN Register SADEN - Slave Address Mask Register (B9h) Reset Value = 0000 0000b Not bit addressable Table 11-2. SADDR Register SADDR - Slave Address Register (A9h) Reset Value = 0000 0000b Not bit addressable

11.3 Baud Rate Selection for UART for Mode 1 and 3

The Baud Rate Generator for transmit and receive cl ocks can be selected separately via the T2CON and BDRCON registers. Figure 11-4. Baud Rate selection 7 6 5 4 3 2 1 0 7 6 5 4 3 2 1 0 RCLK / 16 RBCK INT_BRG TIMER1 TIMER2 INT_BRG TIMER1 TIMER2 TIMER_BRG_RX Rx Clock / 16 0 TIMER_BRG_TX Tx Clock TBCK TCLK

4113C–8051–01/08 AT8xc51Rx2 Table 11-3. Baud Rate Selection Table UART

11.3.1 Internal Baud Rate Generator (BRG)

When the internal Baud Rate Generator is used, the Baud Rates are determined by the BRG overflow depending on the BRL reload value, the val ue of SPD bit (Speed Mode) in BDRCON register and the value of the SMOD1 bit in PCON register. Figure 11-5. Internal Baud Rate

• The baud rate for UART is token by formula: TCLK (T2CON) RCLK (T2CON) TBCK (BDRCON) RBCK (BDRCON) Clock Source UART Tx Clock Source UART Rx 0 0 0 0 Timer 1 Timer 1 1 0 0 0 Timer 2 Timer 1 0 1 0 0 Timer 1 Timer 2 1 1 0 0 Timer 2 Timer 2 X 0 1 0 INT_BRG Timer 1 X 1 1 0 INT_BRG Timer 2

0 X 0 1 Timer 1 INT_BRG

1 X 0 1 Timer 2 INT_BRG

X X 1 1 INT_BRG INT_BRG Peripheral clock BRG 0 BRL INT_BRG BRR auto reload counter overflow SPD B a ud R at e 2S M O D FC L K P E R I P H × B R L ( ) 256 2S M O D 1 FC L K P E R I P H ×

4113C–8051–01/08 AT8xc51Rx2 Table 11-4. SCON Register SCON - Serial Control Register (98h) Reset Value = 0000 0000b Bit addressable 7 6 5 4 3 2 1 0 FE/SM0 SM1 SM2 REN TB8 RB8 TI RI Bit Number Bit Mnemonic Description 7 FE Framing Error bit (SMOD0 = 1 ) Clear to reset the error state, not cleared by a va lid stop bit. Set by hardware when an invalid stop bit is detecte d. SMOD0 must be set to enable access to the FE bit SM0 Serial port Mode bit 0 Refer to SM1 for serial port mode selection. SMOD0 must be cleared to enable access to the SM0 b it

6 SM1

SM1 Mode Description Baud Rat e 0 0Shift Registerf CPU PERIPH/6 1 18-bit UARTVariable 0 29-bit UARTf CPU PERIPH /32 or /16 1 39-bit UARTVariable

5 SM2

Serial port Mode 2 bit/Multiprocessor Communication Enable bit Clear to disable multiprocessor communication featu re. Set to enable multiprocessor communication feature in mode 2 and 3, and eventually mode 1. This bit should be cleared in mo de 0.

4 REN

Clear to disable serial reception. Set to enable serial reception.

3 TB8

Transmitter Bit 8/Ninth bit to transmit in modes 2 and 3 o transmit a logic 0 in the 9th bit. Set to transmit a logic 1 in the 9th bit.

2 RB8

Receiver Bit 8/Ninth bit received in modes 2 and 3 Cleared by hardware if 9th bit received is a logic 0. Set by hardware if 9th bit received is a logic 1. In mode 1, if SM2=0, RB8 is the received stop bit. In mode 0 RB8 is not used. 1 TI Transmit Interrupt flag Clear to acknowledge interrupt. Set by hardware at the end of the 8th bit time in m ode 0 or at the beginning of the stop bit in the other modes. 0 RI Receive Interrupt flag Clear to acknowledge interrupt. Set by hardware at the end of the 8th bit time in m ode 0, see Figure 11-2. and Figure 11-3. in the other modes.

4113C–8051–01/08 AT8xc51Rx2 Table 11-5. Example of Computed Value when X2 = 1, SMOD1 = 1, SPD = 1 Table 11-6. Example of Computed Value when X2 = 0, SMOD1 = 0, SPD = 0 The baud rate generator can be used for mode 1 or 3 (see Figure 11-4.), but also for mode 0 for UART, thanks to the bit SRC located in BDRCON register (Table 11-13.)

11.4 UART Registers

Table 11-7. SADEN Register SADEN - Slave Address Mask Register for UART (B9h) Reset Value = 0000 0000b Table 11-8. SADDR Register SADDR - Slave Address Register for UART (A9h) Reset Value = 0000 0000b Baud Rates F OSC =16.384 MHz F OSC =24 MHz BRL Error (%) BRL Error (%) 115200 247 1.23 243 0.16 57600 238 1.23 230 0.16 38400 229 1.23 217 0.16 28800 220 1.23 204 0.16 19200 203 0.63 178 0.16 9600 149 0.31 100 0.16 4800 43 1.23 - - Baud Rates F OSC =16.384 MHz F OSC =24 MHz BRL Error (%) BRL Error (%) 4800 247 1.23 243 0.16 2400 238 1.23 230 0.16 1200 220 1.23 202 3.55 600 185 0.16 152 0.16 7 6 5 4 3 2 1 0 7 6 5 4 3 2 1 0

4113C–8051–01/08 AT8xc51Rx2 Table 11-9. SBUF Register SBUF - Serial Buffer Register for UART (99h) Reset Value = XXXX XXXXb Table 11-10. BRL Register BRL - Baud Rate Reload Register for the internal baud rate generator, UART (9Ah) Reset Value = 0000 0000b 7 6 5 4 3 2 1 0 7 6 5 4 3 2 1 0

4113C–8051–01/08 AT8xc51Rx2 Table 11-11. T2CON Register T2CON - Timer 2 Control Register (C8h) Reset Value = 0000 0000b Bit addressable 7 6 5 4 3 2 1 0 TF2 EXF2 RCLK TCLK EXEN2 TR2 C/T2# CP/RL2# Bit Number Bit Mnemonic Description Must be cleared by software. Set by hardware on Timer 2 overflow, if RCLK=0 and TCLK=0. Set when a capture or a reload is caused by a negative transition on T2EX pin if EXEN2 = 1. When set, causes the CPU to vector to Timer 2 inter rupt routine when Timer 2 interrupt is enabled. Must be cleared by software. EXF2 doesn’t cause an interrupt in Up/down counter mode (DCEN=1) Receive Clock bit for UART Cleared to use timer 1 overflow as receive clock fo r serial port in mode 1 or 3. Set to use Timer 2 overflow as receive clock for se rial port in mode 1 or 3. Transmit Clock bit for UART Cleared to use timer 1 overflow as transmit clock f or serial port in mode 1 or 3. Set to use Timer 2 overflow as transmit clock for s erial port in mode 1 or 3. Timer 2 External Enable bit Cleared to ignore events on T2EX pin for Timer 2 op eration. Set to cause a capture or reload when a negative tr ansition on T2EX pin is detected, if Timer 2 is not used to clock the seria l port. Cleared to turn off Timer 2. Set to turn on Timer 2. Timer/Counter 2 select bit Cleared for timer operation (input from internal cl ock system: F CLK PERIPH ). Set for counter operation (input from T2 input pin, falling edge trigger). Must be 0 for clock out mode. Timer 2 Capture/Reload bit If RCLK = 1 or TCLK = 1, CP/RL2# is ignored and timer is forced to auto-reload on Timer 2 overflow. Cleared to auto-reload on Timer 2 overflows or negative transitions on T2EX pin if EXEN2 = 1. Set to capture on negative transitions on T2EX pin if EXEN2 = 1.

4113C–8051–01/08 AT8xc51Rx2 Table 11-12. PCON Register PCON - Power Control Register (87h) Reset Value = 00X1 0000b Not bit addressable Power-off flag reset value will be 1 only after a power on (cold reset). A warm reset doesn’t affect the value of this bit. 7 6 5 4 3 2 1 0 SMOD1 SMOD0 - POF GF1 GF0 PD IDL Bit Number Bit Mnemonic Description

7 SMOD1 Serial Port Mode bit 1 for UART

Set to select double baud rate in mode 1, 2 or 3.

6 SMOD0

Serial Port Mode bit 0 for UART Cleared to select SM0 bit in SCON register. Set to select FE bit in SCON register. 5 - Reserved The value read from this bit is indeterminate. Do n ot set this bit.

4 POF

Cleared to recognize next reset type. Set by hardware when V CC rises from 0 to its nominal voltage. Can also be s et by software.

3 GF1

Cleared by user for general purpose usage. Set by user for general purpose usage.

2 GF0

Cleared by user for general purpose usage. Set by user for general purpose usage. 1 PD Power-down mode bit Cleared by hardware when reset occurs. Set to enter power-down mode.

0 IDL

Cleared by hardware when interrupt or reset occurs. Set to enter idle mode.

4113C–8051–01/08 AT8xc51Rx2 Table 11-13. BDRCON Register BDRCON - Baud Rate Control Register (9Bh) Reset Value = XXX0 0000b Not bit addressable 7 6 5 4 3 2 1 0 - - - BRR TBCK RBCK SPD SRC Bit Number Bit Mnemonic Description 7 - Reserved The value read from this bit is indeterminate. Do n ot set this bit 6 - Reserved The value read from this bit is indeterminate. Do n ot set this bit 5 - Reserved The value read from this bit is indeterminate. Do n ot set this bit.

4 BRR

Cleared to stop the internal Baud Rate Generator. Set to start the internal Baud Rate Generator.

3 TBCK

Transmission Baud rate Generator Selection bit for UART Cleared to select Timer 1 or Timer 2 for the Baud R ate Generator. Set to select internal Baud Rate Generator.

2 RBCK

Reception Baud Rate Generator Selection bit for UART Cleared to select Timer 1 or Timer 2 for the Baud R ate Generator. Set to select internal Baud Rate Generator.

1 SPD

Baud Rate Speed Control bit for UART Cleared to select the SLOW Baud Rate Generator. Set to select the FAST Baud Rate Generator.

0 SRC

Baud Rate Source select bit in Mode 0 for UART Cleared to select F OSC /12 as the Baud Rate Generator (F CLK PERIPH /6 in X2 mode). Set to select the internal Baud Rate Generator for UARTs in mode 0.

4113C–8051–01/08 AT8xc51Rx2 12. Interrupt System The AT8xc51Rx2 have a total of 8 interrupt vectors: two external interrupts (INT0 and INT1 ), three timer interrupts (timers 0, 1 and 2), the ser ial port interrupt, Keyboard interrupt and the PCA global interrupt. These interrupts are shown in Figure 12-1. Figure 12-1. Interrupt Control System Each of the interrupt sources can be individually e nabled or disabled by setting or clearing a bit in the Interrupt Enable register ( Table 12-5 and Table 12-3 ). This register also contains a global disable bit, which must be cleared to disable all interrupts at once. Each interrupt source also can be individually prog rammed to one out of four priority levels by setting or clearing a bit in the Interrupt Priority register ( Table 12-6 ) and in the Interrupt Priority High register ( Table 12-4 and Table 12-5 ) shows the bit values and priority levels associat ed with each combination.

12.1 Registers

The PCA interrupt vector is located at address 0033 H, the Keyboard interrupt vector is located at address 004BH. All other vectors addresses are the same as standard C52 devices. IE1 High Priority Interrupt Interrupt Polling Sequence, Decreasing from High to Low Priority Low Priority Interrupt Global Disable Individual Enable EXF2 TF2 TI RI TF0 INT0 INT1 TF1 IPH, IPL IE0 PCA IT KBD IT

4113C–8051–01/08 AT8xc51Rx2 Table 12-1. Priority Level Bit Values A low-priority interrupt can be interrupted by a high priority interrupt, but not by another low-prior- ity interrupt. A high-priority interrupt can’t be interrupted by any other interrupt source. If two interrupt requests of different priority lev els are received simultaneously, the request of higher priority level is serviced. If interrupt requests of the same priority level are received simul- taneously, an internal polling sequence determines which request is serviced. Thus within each priority level there is a second priority structure determined by the polling sequence. Table 12-2. IEO Register IE0 - Interrupt Enable Register (A8h) IPH.x IPL.x Interrupt Level Priority 0 0 0 (Lowest) 0 1 1 1 0 2 1 1 3 (Highest) 7 6 5 4 3 2 1 0 EA EC ET2 ES ET1 EX1 ET0 EX0 Bit Number Bit Mnemonic Description 7 EA Enable All interrupt bit Cleared to disable all interrupts. Set to enable all interrupts. 6 EC PCA interrupt enable bit Cleared to disable. Set to enable.

5 ET2

Timer 2 overflow interrupt enable bit Cleared to disable Timer 2 overflow interrupt. Set to enable Timer 2 overflow interrupt. 4 ES Serial port enable bit Cleared to disable serial port interrupt. Set to enable serial port interrupt.

3 ET1

Timer 1 overflow interrupt enable bit Cleared to disable timer 1 overflow interrupt. Set to enable timer 1 overflow interrupt.

2 EX1

External interrupt 1 enable bit Cleared to disable external interrupt 1. Set to enable external interrupt 1.

1 ET0

Timer 0 overflow interrupt enable bit Cleared to disable timer 0 overflow interrupt. Set to enable timer 0 overflow interrupt.

0 EX0

External interrupt 0 enable bit Cleared to disable external interrupt 0. Set to enable external interrupt 0.

4113C–8051–01/08 AT8xc51Rx2 Reset Value = 0000 0000b Bit addressable Table 12-3. IPL0 Register IPL0 - Interrupt Priority Register (B8h) Reset Value = X000 0000b Bit addressable Table 12-4. IPH0 Register IPH0 - Interrupt Priority High Register (B7h) 7 6 5 4 3 2 1 0 - PPCL PT2L PSL PT1L PX1L PT0L PX0L Bit Number Bit Mnemonic Description 7 - Reserved The value read from this bit is indeterminate. Do n ot set this bit.

6 PPCL PCA interrupt priority bit

Refer to PPCH for priority level.

5 PT2L Timer 2 overflow interrupt priority bit

Refer to PT2H for priority level.

4 PSL Serial port priority bit

Refer to PSH for priority level.

3 PT1L Timer 1 overflow interrupt priority bit

Refer to PT1H for priority level.

2 PX1L External interrupt 1 priority bit

Refer to PX1H for priority level.

1 PT0L Timer 0 overflow interrupt priority bit

Refer to PT0H for priority level.

0 PX0L External interrupt 0 priority bit

Refer to PX0H for priority level. 7 6 5 4 3 2 1 0 - PPCH PT2H PSH PT1H PX1H PT0H PX0H

4113C–8051–01/08 AT8xc51Rx2 Reset Value = X000 0000b Not bit addressable Table 12-5. IE1 Register IE1 - Interrupt Enable Register (B1h) Bit Number Bit Mnemonic Description 7 - Reserved The value read from this bit is indeterminate. Do n ot set this bit.

6 PPCH

PCA interrupt priority high bit. PPCH PPCL Priority Level 0 0Lowest 0 1 1 0 1 1Highest

5 PT2H

Timer 2 overflow interrupt priority high bit PT2H PT2L Priority Level 0 0Lowest 0 1 1 0 1 1Highest

4 PSH

Serial port priority high bit PSH PSL Priority Level 0 0Lowest 0 1 1 0 1 1Highest

3 PT1H

Timer 1 overflow interrupt priority high bit PT1H PT1L Priority Level 0 0 Lowest 0 1 1 0 1 1 Highest

2 PX1H

External interrupt 1 priority high bit PX1H PX1L Priority Level 0 0Lowest 0 1 1 0 1 1Highest

1 PT0H

Timer 0 overflow interrupt priority high bit PT0H PT0L Priority Level 0 0Lowest 0 1 1 0 1 1Highest

0 PX0H

External interrupt 0 priority high bit PX0H PX0L Priority Level 0 0Lowest 0 1 1 0 1 1Highest 7 6 5 4 3 2 1 0 - - - - - - - KBD

4113C–8051–01/08 AT8xc51Rx2 Reset Value = XXXX XXX0b Bit addressable Table 12-6. IPL1 Register IPL1 - Interrupt Priority Register (B2h) Reset Value = XXXX XXX0b Bit addressable Table 12-7. IPH1 Register Bit Number Bit Mnemonic Description 7 - Reserved 6 - Reserved 5 - Reserved 4 - Reserved 3 - Reserved 2 - Reserved 1 - Reserved

0 KBD

Keyboard interrupt Enable bit Cleared to disable keyboard interrupt. Set to enable keyboard interrupt. 7 6 5 4 3 2 1 0 - - - - - - - KBDL Bit Number Bit Mnemonic Description 7 - Reserved The value read from this bit is indeterminate. Do n ot set this bit. 6 - Reserved The value read from this bit is indeterminate. Do n ot set this bit. 5 - Reserved The value read from this bit is indeterminate. Do n ot set this bit. 4 - Reserved The value read from this bit is indeterminate. Do n ot set this bit. 3 - Reserved The value read from this bit is indeterminate. Do n ot set this bit. 2 - Reserved The value read from this bit is indeterminate. Do n ot set this bit. 1 - Reserved The value read from this bit is indeterminate. Do n ot set this bit.

0 KBDL Keyboard Interrupt Priority bit

Refer to KBDH for priority level.

4113C–8051–01/08 AT8xc51Rx2 IPH1 - Interrupt Priority High Register (B3h) Reset Value = XXXX XXX0b Not bit addressable

12.2 Interrupt Sources and Vector Addresses

Table 12-8. Interrupt Sources and Vector Addresses 7 6 5 4 3 2 1 0 - - - - - - - KBDH Bit Number Bit Mnemonic Description 7 - Reserved The value read from this bit is indeterminate. Do n ot set this bit. 6 - Reserved The value read from this bit is indeterminate. Do n ot set this bit. 5 - Reserved The value read from this bit is indeterminate. Do n ot set this bit. 4 - Reserved The value read from this bit is indeterminate. Do n ot set this bit. 3 - Reserved The value read from this bit is indeterminate. Do n ot set this bit. 2 - Reserved The value read from this bit is indeterminate. Do n ot set this bit. 1 - Reserved The value read from this bit is indeterminate. Do n ot set this bit.

0 KBDH

Keyboard interrupt Priority High bit KB DH KBDL Priority Level 0 0 Lowest 0 1 1 0 1 1 Highest Number Polling Priority Interrupt Source Interrupt Request Vector Address 0 0 Reset 0000h 1 1 INT0 IE0 0003h 2 2 Timer 0 TF0 000Bh 3 3 INT1 IE1 0013h 4 4 Timer 1 IF1 001Bh 5 6 UART RI+TI 0023h 6 7 Timer 2 TF2+EXF2 002Bh 7 5 PCA CF + CCFn (n = 0-4) 0033h 8 8 Keyboard KBDIT 003Bh

4113C–8051–01/08 AT8xc51Rx2

4113C–8051–01/08 AT8xc51Rx2 13. Keyboard Interface The AT8xc51Rx2 implement a keyboard interface allow ing the connection of a 8 x n matrix key- board. It is based on 8 inputs with programmable in terrupt capability on both high or low level. These inputs are available as alternate function of P1 and allow to exit from idle and power- down modes. The keyboard interfaces with the C51 core through 3 special function registers: KBLS, the Key- board Level Selection register (Table 13-3), KBE, Th e Keyboard Interrupt Enable register (Table 13-2), and KBF, the Keyboard Flag register (Table 13-1).

13.0.1 Interrupt

The keyboard inputs are considered as 8 independent interrupt sources sharing the same inter- rupt vector. An interrupt enable bit (KBD in IE1) a llows global enable or disable of the keyboard interrupt (see Figure 13-1). As detailed in Figure 13 -2 each keyboard input has the capability to detect a programmable level according to KBLS.x bit value. Level detection is then reported in interrupt flags KBF.x that can be masked by software using KBE.x bits. This structure allow keyboard arrangement from 1 x n to 8 x n matrix and allows usage of P1 inputs for other purpose. Figure 13-1. Keyboard Interface Block Diagram Figure 13-2. Keyboard Input Circuitry

13.0.2 Power Reduction Mode

P1 inputs allow exit from idle and power-down modes as detailed in Section “Power-down Mode”, page 56. P1:x KBE.x KBF.x KBLS.x VCC Internal Pull-up P1.0 Keyboard Interface Interrupt Request KBD IE1 Input Circuitry P1.1 Input Circuitry P1.2 Input Circuitry P1.3 Input Circuitry P1.4 Input Circuitry P1.5 Input Circuitry P1.6 Input Circuitry P1.7 Input Circuitry KBDIT

4113C–8051–01/08 AT8xc51Rx2

13.1 Registers

Table 13-1. KBF Register KBF - Keyboard Flag Register (9Eh) Reset Value = 0000 0000b 7 6 5 4 3 2 1 0 KBF7 KBF6 KBF5 KBF4 KBF3 KBF2 KBF1 KBF0 Bit Number Bit Mnemonic Description

7 KBF7

Set by hardware when the Port line 7 detects a programmed level. It generates a Keyboard interrupt request if the KBKBIE.7 bit in K BIE register is set. Must be cleared by software.

6 KBF6

Set by hardware when the Port line 6 detects a programmed level. It generates a Keyboard interrupt request if the KBIE.6 bit in KBI E register is set. Must be cleared by software.

5 KBF5

Set by hardware when the Port line 5 detects a programmed level. It generates a Keyboard interrupt request if the KBIE.5 bit in KBI E register is set. Must be cleared by software.

4 KBF4

Set by hardware when the Port line 4 detects a programmed level. It generates a Keyboard interrupt request if the KBIE.4 bit in KBI E register is set. Must be cleared by software.

3 KBF3

Set by hardware when the Port line 3 detects a programmed level. It generates a Keyboard interrupt request if the KBIE.3 bit in KBI E register is set. Must be cleared by software.

2 KBF2

Set by hardware when the Port line 2 detects a programmed level. It generates a Keyboard interrupt request if the KBIE.2 bit in KBI E register is set. Must be cleared by software.

1 KBF1

Set by hardware when the Port line 1 detects a programmed level. It generates a Keyboard interrupt request if the KBIE.1 bit in KBI E register is set. Must be cleared by software.

0 KBF0

Set by hardware when the Port line 0 detects a programmed level. It generates a Keyboard interrupt request if the KBIE.0 bit in KBI E register is set. Must be cleared by software.

4113C–8051–01/08 AT8xc51Rx2 Table 13-2. KBE Register KBE - Keyboard Input Enable Register (9Dh) Reset Value = 0000 0000b 7 6 5 4 3 2 1 0 KBE7 KBE6 KBE5 KBE4 KBE3 KBE2 KBE1 KBE0 Bit Number Bit Mnemonic Description

7 KBE7

Keyboard line 7 enable bit Cleared to enable standard I/O pin. Set to enable KBF.7 bit in KBF register to generate an interrupt request.

6 KBE6

Keyboard line 6 enable bit Cleared to enable standard I/O pin. Set to enable KBF.6 bit in KBF register to generate an interrupt request.

5 KBE5

Keyboard line 5 enable bit Cleared to enable standard I/O pin. Set to enable KBF.5 bit in KBF register to generate an interrupt request.

4 KBE4

Keyboard line 4 enable bit Cleared to enable standard I/O pin. Set to enable KBF.4 bit in KBF register to generate an interrupt request.

3 KBE3

Keyboard line 3 enable bit Cleared to enable standard I/O pin. Set to enable KBF.3 bit in KBF register to generate an interrupt request.

2 KBE2

Keyboard line 2 enable bit Cleared to enable standard I/O pin. Set to enable KBF.2 bit in KBF register to generate an interrupt request.

1 KBE1

Keyboard line 1 enable bit Cleared to enable standard I/O pin. Set to enable KBF.1 bit in KBF register to generate an interrupt request.

0 KBE0

Keyboard line 0 enable bit Cleared to enable standard I/O pin. Set to enable KBF.0 bit in KBF register to generate an interrupt request.

4113C–8051–01/08 AT8xc51Rx2 Table 13-3. KBLS Register KBLS - Keyboard Level Selector Register (9Ch) Reset Value = 0000 0000b 7 6 5 4 3 2 1 0 KBLS7 KBLS6 KBLS5 KBLS4 KBLS3 KBLS2 KBLS1 KBLS0 Bit Number Bit Mnemonic Description

7 KBLS7

Keyboard line 7 level selection bit Cleared to enable a low level detection on Port lin e 7. Set to enable a high level detection on Port line 7 .

6 KBLS6

Keyboard line 6 level selection bit Cleared to enable a low level detection on Port lin e 6. Set to enable a high level detection on Port line 6 .

5 KBLS5

Keyboard line 5 level selection bit Cleared to enable a low level detection on Port lin e 5. Set to enable a high level detection on Port line 5 .

4 KBLS4

Keyboard line 4 level selection bit Cleared to enable a low level detection on Port lin e 4. Set to enable a high level detection on Port line 4 .

3 KBLS3

Keyboard line 3 level selection bit Cleared to enable a low level detection on Port lin e 3. Set to enable a high level detection on Port line 3 .

2 KBLS2

Keyboard line 2 level selection bit Cleared to enable a low level detection on Port lin e 2. Set to enable a high level detection on Port line 2 .

1 KBLS1

Keyboard line 1 level selection bit Cleared to enable a low level detection on Port lin e 1. Set to enable a high level detection on Port line 1 .

0 KBLS0

Keyboard line 0 level selection bit Cleared to enable a low level detection on Port lin e 0. Set to enable a high level detection on Port line 0 .

4113C–8051–01/08 AT8xc51Rx2 14. Power Management

14.1 Idle Mode

An instruction that sets PCON.0 indicates that it i s the last instruction to be executed before going into Idle mode. In Idle mode, the internal clock signal is gated off to the CPU, but not to the interrupt, Timer, and Serial Port functions. The CPU status is preserved in its entirety: the Stack Pointer, Program Counter, Program Status Word, Accu mulator and all other registers maintain their data during idle. The port pins hold the logi cal states they had at the time Idle was acti- vated. ALE and PSEN hold at logic high level. There are two ways to terminate the Idle mode. Acti vation of any enabled interrupt will cause PCON.0 to be cleared by hardware, terminating the I dle mode. The interrupt will be serviced, and following RETI the next instruction to be execu ted will be the one following the instruction that put the device into idle. The flag bits GF0 and GF1 can be used to give an in dication if an interrupt occurred during nor- mal operation or during idle. For example, an instr uction that activates idle can also set one or both flag bits. When idle is terminated by an inter rupt, the interrupt service routine can examine the flag bits. The other way of terminating the Idle mode is with a hardware reset. Since the clock oscillator is still running, the hardware reset needs to be held active for only two machine cycles (24 oscilla- tor periods) to complete the reset.

14.2 Power-down Mode

To save maximum power, a power-down mode can be inv oked by software (refer to Table 11- 12 , PCON register). In power-down mode, the oscillator is stopped and t he instruction that invoked power-down mode is the last instruction executed. The internal RAM and SFRs retain their value until the power-down mode is terminated. V CC can be lowered to save further power. Either a har dware reset or an external interrupt can cause an exit fr om power-down. To properly terminate power- down, the reset or external interrupt should not be executed before V CC is restored to its normal operating level and must be held active long enough for the oscillator to restart and stabilize. Only external interrupts INT0 , INT1 and Keyboard Interrupts are useful to exit from power-down. Thus, the interrupt must be enabled and configured as level - or edge - sensitive interrupt input. When Keyboard Interrupt occurs after a power-down mode, 1024 clocks are necessary to exit to power-down mode and enter in operating mode. Holding the pin low restarts the oscillator but bringing the pin high completes the exit as detailed in Figure 14-1 . When both interrupts are enabled, the oscillator restarts as soon as one of the two inputs is held low and power-down exit will be completed when the first input is released. In this case, the higher priority interrupt service ro utine is executed. Once the interrupt is serviced, the next instruction to be executed after RETI will be the one following the instruction that put AT8xc51Rx2 into power-down mode.

4113C–8051–01/08 AT8xc51Rx2 Figure 14-1. Power-down Exit Waveform Exit from power-down by reset redefines all the SFR s, exit from power-down by external inter- rupt does no affect the SFRs. Exit from power-down by either reset or external in terrupt does not affect the internal RAM content. Note: If idle mode is activated with power-down mode (ID L and PD bits set), the exit sequence is unchanged, when execution is vectored to interrupt, PD and IDL bits are cleared and idle mode is not entered. Table 14-1 shows the state of ports during idle and power-down modes. Note: 1. Port 0 can force a 0 level. A "one" will leave port floating. INT1 INT0 XTAL Power-down Phase OscillatoR Restart Active Phase Active Phase Table 14-1. State of Ports Mode Program Memory ALE PSEN PORT0 PORT1 PORT2 PORT3 Idle Internal 1 1 Port Data (1) Port Data Port Data Port Data Idle External 1 1 Floating Port Data Address Port Data Power-down Internal 0 0 Port Dat (1) Port Data Port Data Port Data Power-down External 0 0 Floating Port Data Port Data Port Data

4113C–8051–01/08 AT8xc51Rx2 15. Hardware Watchdog Timer The WDT is intended as a recovery method in situati ons where the CPU may be subjected to software upset. The WDT consists of a 14-bit counte r and the WatchDog Timer Reset (WDTRST) SFR. The WDT is by default disabled from e xiting reset. To enable the WDT, user must write 01EH and 0E1H in sequence to the WDTRST, SFR location 0A6H. When WDT is enabled, it will increment every machine cycle while the oscillator is running and there is no way to disable the WDT except through reset (either har dware reset or WDT overflow reset). When WDT overflows, it will drive an output RESET HIGH pulse at the RST-pin.

15.1 Using the WDT

To enable the WDT, user must write 01EH and 0E1H in sequence to the WDTRST, SFR loca- tion 0A6H. When WDT is enabled, the user needs to s ervice it by writing to 01EH and 0E1H to WDTRST to avoid WDT overflow. The 14-bit counter ov erflows when it reaches 16383 (3FFFH) and this will reset the device. When WDT is enabled, it will increment every machine cycle while the oscillator is running. Therefore, the user must reset the WDT at least every 16383 machine cycles. To reset the WDT the user must write 01EH a nd 0E1H to WDTRST. WDTRST is a write only register. The WDT counter cannot be read or written. When WDT overflows, it will generate an output RESET pulse at the RST-pin. The RESET pul se duration is 96 x T CLK PERIPH , where TCLK PERIPH = 1/F CLK PERIPH . To make the best use of the WDT, it should be serviced in those sec- tions of code that will periodically be executed within the time required to prevent a WDT reset. To have a more powerful WDT, a 2 7 counter has been added to extend the Time-out capa bility, ranking from 16 ms to 2s @ F osc = 12 MHz. To manage this feature, refer to WDTPRG register description, Table 15-1 . Table 15-1. WDTRST Register WDTRST - Watchdog Reset Register (0A6h) Reset Value = XXXX XXXXb Write only, this SFR is used to reset/enable the WDT by writing 01EH then 0E1H in sequence. 7 6 5 4 3 2 1 0 - - - - - - - -

4113C–8051–01/08 AT8xc51Rx2 Table 15-2. WDTPRG Register WDTPRG - Watchdog Timer Out Register (0A7h) Reset Value = XXXX X000

15.2 WDT During Power-down and Idle

In Power-down mode the oscillator stops, which mean s the WDT also stops. While in Power- down mode the user does not need to service the WDT . There are 2 methods of exiting Power- down mode: by a hardware reset or via a level activated external interrupt which is enabled prior to entering Power-down mode. When Power-down is exi ted with hardware reset, servicing the WDT should occur as normal, whenever the AT8xc51Rx2 is reset. Exiting Power-down with an interrupt is significantly different. The interrupt is held low long enough for the oscillator to stab i- lize. When the interrupt is brought high, the inter rupt is serviced. To prevent the WDT from resetting the device while the interrupt pin is held low, the WDT is not started until the interrupt is pulled high. It is suggested that the WDT be reset during the interrupt service routine. To ensure that the WDT does not overflow within a few states of exiting of power-down, it is bet- ter to reset the WDT just before entering power-down. In the Idle mode, the oscillator continues to run. To prevent the WDT from resetting the AT8xc51Rx2 while in Idle mode, the user should alwa ys set up a timer that will periodically exit Idle, service the WDT, and re-enter Idle mode. 7 6 5 4 3 2 1 0 - - - - - S2 S1 S0 Bit Number Bit Mnemonic Description 7 - Reserved The value read from this bit is undetermined. Do no t try to set this bit. 6 - 5 - 4 - 3 - 2 S2 WDT Time-out select bit 2

1 S1 WDT Time-out select bit 1

0 S0 WDT Time-out select bit 0

0 0 0 (2 14 - 1) machine cycles, 16. 3 ms @ F osc =12 MHz 0 0 1 (2 15 - 1) machine cycles, 32.7 ms @ F osc =12 MHz 0 1 0 (2 16 - 1) machine cycles, 65. 5 ms @ F osc =12 MHz 0 1 1 (2 17 - 1) machine cycles, 131 ms @ F osc =12 MHz 1 0 0 (2 18 - 1) machine cycles, 262 ms @ F osc =12 MHz 1 0 1 (2 19 - 1) machine cycles, 542 ms @ F osc =12 MHz 1 1 0 (2 20 - 1) machine cycles, 1.05 s @ F osc =12 MHz 1 1 1 (2 21 - 1) machine cycles, 2.09 s @ F osc =12 MHz

4113C–8051–01/08 AT8xc51Rx2 16. ROM

16.1 ROM Structure

The T89C51RB2/RC2 ROM memory is divided in two different arrays:

• The code array:16/32K bytes.
• The config byte: 1 byte.

16.1.1 Hardware Config Byte

The config byte sets the starting microcontroller options and the security levels. The starting options are X2 mode, and XRAM.

16.2 ROM Lock System

The program Lock system, when programmed, protects the on-chip program against software piracy. 7 6 5 4 3 2 1 0 X2 - - - XRAM - LB1 LB0 Bit Number Bit Mnemonic Description 7 X2 X2 Mode Cleared to force X2 mode (6 clocks per instruction) Set to force X1 mode, Standard Mode. 6 - Reserved 5 - Reserved 4 - Reserved

3 XRAM

Set this bit to enable XRAM. Clear this bit to disable XRAM. 2 - Reserved 1-0 LB0-1 User Program ROM Lock Bits see Table 16-1.

4113C–8051–01/08 AT8xc51Rx2

16.2.1 Program ROM Lock Bits

Notes: 1. U: unprogrammed P: programmed 2. The lock bits when programmed according to Table 16-1 will provide different level of protec- tion for the on-chip code and data. Table 16-1. Program Lock bits Program Lock Bits Protection Description Security level LB0 LB1 1 U U No program lock features enabled. 2 P U Reserved. Do not use.

3 U P

MOVC instruction executed from external program mem ory are disabled from fetching code bytes from internal memory, EA is sampled and latched on reset. Verify disable.

4113C–8051–01/08 AT8xc51Rx2 17. Power-off Flag The Power-off flag allows the user to distinguish b etween a “cold start” reset and a “warm start” reset. A cold start reset is the one induced by V CC switch-on. A warm start reset occurs while V CC is still applied to the device and could be generated for example by an exit from power-down. The Power-off flag (POF) is located in PCON registe r (Table 17-1). POF is set by hardware when V CC rises from 0 to its nominal voltage. The POF can b e set or cleared by software allow- ing the user to determine the type of reset. Table 17-1. PCON Register PCON - Power Control Register (87h) Reset Value = 00X1 0000b Not bit addressable 7 6 5 4 3 2 1 0 SMOD1 SMOD0 - POF GF1 GF0 PD IDL Bit Number Bit Mnemonic Description

7 SMOD1 Serial port Mode bit 1

Set to select double baud rate in mode 1, 2 or 3. Cleared to select SM0 bit in SCON register. Set to select FE bit in SCON register. 5 - Reserved The value read from this bit is indeterminate. Do not set this bit. Cleared to recognize next reset type. Set by hardware when V CC rises from 0 to its nominal voltage. Can also be set by software. Cleared by user for general purpose usage. Set by user for general purpose usage. Cleared by user for general purpose usage. Set by user for general purpose usage. 1 PD Power-down mode bit Cleared by hardware when reset occurs. Set to enter power-down mode. Cleared by hardware when interrupt or reset occurs. Set to enter idle mode.

4113C–8051–01/08 AT8xc51Rx2 18. Reduced EMI Mode The ALE signal is used to demultiplex address and d ata buses on port 0 when used with exter- nal program or data memory. Nevertheless, during in ternal code execution, ALE signal is still generated. In order to reduce EMI, ALE signal can be disabled by setting AO bit. The AO bit is located in AUXR register at bit locat ion 0. As soon as AO is set, ALE is no longer output but remains active during MOVX and MOVC inst ructions and external fetches. During ALE disabling, ALE pin is weakly pulled high. Table 18-1. AUXR Register AUXR - Auxiliary Register (8Eh) 7 6 5 4 3 2 1 0 - - M0 - XRS1 XRS0 EXTRAM AO Bit Number Bit Mnemonic Description 7 - Reserved The value read from this bit is indeterminate. Do n ot set this bit 6 - Reserved The value read from this bit is indeterminate. Do n ot set this bit 5 M0 Pulse length Cleared to stretch MOVX control: the RD and the WR pulse length is 6 clock periods (default). Set to stretch MOVX control: the RD and the WR pulse length is 30 clock periods. 4 - Reserved The value read from this bit is indeterminate. Do n ot set this bit 0 0256 bytes (default) 0 1512 bytes 1 0768 bytes 1 11024 bytes Cleared to access internal XRAM using movx @ Ri/ @ DPTR. Set to access external memory. Programmed by hardware after Power-up regarding Har dware Security Byte (HSB), default setting, XRAM selected. 0 AO ALE Output bit Cleared, ALE is emitted at a constant rate of 1/6 the oscillator frequency (or 1/3 if X2 mode is used) (default). Set, ALE is active only during a MOVX or MOVC instructione is used.

4113C–8051–01/08 AT8xc51Rx2 19. Electrical Characteristics

19.1 DC Parameters for Standard Voltage

TA = 0 °C to +70 °C; V SS = 0V; V CC = 4.5V to 5.5V; F = 10 to 40 MHz TA = -40 °C to +85 °C; V SS = 0V; V CC =4.5V to 5.5V; F = 10 to 40 MHz Table 19-1. Absolute Maximum Ratings Note: Stresses at or above those listed under “Absolu te Maximum Ratings” may cause permanent damage to the device. This is a stress rating only and functi onal operation of the device at these or any other condi - tions above those indicated in the operational sections of this specification is not implied. Exposure to a bso- lute maximum rating conditions may affect device reliability. Power dissipation value is based on the maximum allowable die temperature and the thermal resistanc e of the package. Symbol Parameter Min Typ Max Unit Test Conditions VIL Input Low Voltage -0.5 0.2 V CC - 0.1 V VIH Input High Voltage except RST, XTAL1 0.2 V CC + 0.9 V CC + 0.5 V VIH1 Input High Voltage RST, XTAL1 0.7 V CC VCC + 0.5 V VOL Output Low Voltage, ports 1, 2, 3, 4 (6) 0.3 0.45 1.0 V V V I OL = 100 µ A(4) IOL = 1.6 mA (4) IOL = 3.5 mA (4) VOL1 Output Low Voltage, port 0, ALE, PSEN (6) 0.3 0.45 1.0 V V V I OL = 200 µ A(4) IOL = 3.2 mA (4) IOL = 7.0 mA (4) VOH Output High Voltage, ports 1, 2, 3, 4 VCC - 0.3 VCC - 0.7 VCC - 1.5 V V V I OH = -10 µ A IOH = -30 µ A IOH = -60 µ A VCC = 5V ± 10% VOH1 Output High Voltage, port 0, ALE, PSEN VCC - 0.3 VCC - 0.7 VCC - 1.5 V V V I OH = -200 µ A IOH = -3.2 mA IOH = -7.0 mA VCC = 5V ± 10% RRST RST Pull-down Resistor 50 200 (5) 250 k Ω IIL Logical 0 Input Current ports 1, 2, 3, 4 and 5 -50 µ A V IN = 0.45V ILI Input Leakage Current ±10 µ A 0.45V < V IN < V CC ITL Logical 1 to 0 Transition Current, ports 1, 2, 3, 4 -650 µ A V IN = 2.0 V CIO Capacitance of I/O Buffer 10 pF Fc = 3 MHz T A = 25 °C IPD Power-down Current 100 150 µ A 4.5V < V CC < 5.5V (3) ICCOP Power Supply Current on normal mode 0.29 x Frequency (MHz) + 4 mA V CC = 5.5V (1) ICCIDLE Power Supply Current on idle mode 0.16 x Frequency (MHz) + 4 mA V CC = 5.5V (2)

4113C–8051–01/08 AT8xc51Rx2

19.2 DC Parameters for Standard Voltage (2)

TA = 0 °C to +70 °C; V SS = 0 V; V CC = 2.7V to 5.5V; F = 10 to 40 MHz TA = -40 °C to +85 °C; V SS = 0 V; V CC = 2.7V to 5.5V; F = 10 to 40 MHz Symbol Parameter Min Typ (5) Max Unit Test Conditions VIL Input Low Voltage -0.5 0.2 V CC - 0.1 V VIH Input High Voltage except XTAL1, RST 0.2 V CC + 0.9 V CC + 0.5 V VIH1 Input High Voltage, XTAL1, RST 0.7 V CC VCC + 0.5 V VOL Output Low Voltage, ports 1, 2, 3, 4 and 5 (6) 0.45 V I OL = 0.8 mA (4) VOL1 Output Low Voltage, port 0, ALE, PSEN (6) 0.45 V I OL = 1.6 mA (4) VOH Output High Voltage, ports 1, 2, 3, 4 and 5 0.9 V CC V I OH = -10 µ A VOH1 Output High Voltage, port 0, ALE, PSEN 0.9 V CC V I OH = -40 µ A IIL Logical 0 Input Current ports 1, 2, 3, 4 and 5 -50 µ A V IN = 0.45V ILI Input Leakage Current ±10 µ A 0.45V < V IN < V CC ITL Logical 1 to 0 Transition Current, ports 1, 2, 3, 4 and 5 -650 µ A V IN = 2.0V RRST RST Pulldown Resistor 50 200 250 k Ω CIO Capacitance of I/O Buffer 10 pF Fc = 3 MHz T A = 25 °C IPD Power-down Current 120 150 µ A V CC =2.7V to 5.5V (3) ICCOP Power Supply Current on normal mode 0.29 x Frequency (MHz) + 4 mA V CC = 5.5V (1) ICCIDLE Power Supply Current on idle mode 0.16 x Frequency (MHz) + 4 mA V CC = 5.5V (2)

4113C–8051–01/08 AT8xc51Rx2

19.3 DC Parameters for Low Voltage

TA = 0 °C to +70 °C; V SS = 0V; V CC = 2.7V to 3.6V; F = 10 to 40 MHz TA = -40 °C to +85 °C; V SS = 0V; V CC = 2.7V to 3.6V; F = 10 to 40 MHz Notes: 1. Operating I CC is measured with all output pins disconnected; XTAL1 driven with T CLCH , T CHCL = 5 ns (see Figure 19-4.), VIL = V SS + 0.5V, VIH = V CC - 0.5V; XTAL2 N.C.; EA = RST = Port 0 = V CC . I CC would be slightly higher if a crystal oscillator us ed (see Figure 19-1 ). 2. Idle I CC is measured with all output pins disconnected; XTAL1 driven with T CLCH , T CHCL = 5 ns, V IL = V SS + 0.5V, VIH = V CC - 0.5V; XTAL2 N.C; Port 0 = V CC ; EA = RST = V SS (see Figure 19-2 ). 3. Power-down I CC is measured with all output pins disconnected; EA = V SS , PORT 0 = V CC ; XTAL2 NC.; RST = V SS (see Fig- ure 19-3 ). 4. Capacitance loading on Ports 0 and 2 may cause spu rious noise pulses to be superimposed on the V OL s of ALE and Ports 1 and 3. The noise is due to external bus capacitance discharging into the Port 0 and Port 2 pins when these pins make 1 to 0 transitions during bus operation. In the worst cases (capacitive loading 100pF), the noise pulse on the ALE line may exceed 0.45V with maxi V OL peak 0.6V. A Schmitt Trigger use is not necessary. 5. Typical are based on a limited number of samples and are not guaranteed. The values listed are at ro om temperature and 5V. 6. Under steady state (non-transient) conditions, I OL must be externally limited as follows: Maximum I OL per port pin: 10 mA Maximum I OL per 8-bit port: Port 0: 26 mA Ports 1, 2 and 3: 15 mA Maximum total I OL for all output pins: 71 mA If I OL exceeds the test condition, V OL may exceed the related specification. Pins are not guaranteed to sink current greater than the listed test conditions. 7. For other values, please contact your sales offic e. Symbol Parameter Min Typ Max Unit Test Conditions VIL Input Low Voltage -0.5 0.2 V CC - 0.1 V VIH Input High Voltage except RST, XTAL1 0.2 V CC + 0.9 V CC + 0.5 V VIH1 Input High Voltage, RST, XTAL1 0.7 V CC VCC + 0.5 V VOL Output Low Voltage, ports 1, 2, 3, 4 (6) 0.45 V I OL = 0.8 mA (4) VOL1 Output Low Voltage, port 0, ALE, PSEN (6) 0.45 V I OL = 1.6 mA (4) VOH Output High Voltage, ports 1, 2, 3, 4 0.9 V CC V I OH = -10 µ A VOH1 Output High Voltage, port 0, ALE, PSEN 0.9 V CC V I OH = -40 µ A IIL Logical 0 Input Current ports 1, 2, 3, 4 -50 µ A V IN = 0.45V ILI Input Leakage Current ±10 µ A 0.45V < V IN < V CC ITL Logical 1 to 0 Transition Current, ports 1, 2, 3, -650 µ A V IN = 2.0V RRST RST Pulldown Resistor 50 200 (5) 250 k Ω CIO Capacitance of I/O Buffer 10 pF Fc = 3 MHz T A = 25 °C IPD Power-down Current 10 (5) 50 µ A VCC = 2.7V to 3.6V (3) ICCOP Power Supply Current on normal mode 0.31 x Frequency (MHz) + 4 mA V CC = 3.6V (1) ICCIDLE Power Supply Current on idle mode 0.2 x Frequency (MHz) + 4 mA V CC = 3.6V (2)

4113C–8051–01/08 AT8xc51Rx2

19.4 AC Parameters

19.4.1 Explanation of the AC Symbols

Each timing symbol has 5 characters. The first char acter is always a “t” (stands for time). The other characters, depending on their positions, sta nd for the name of a signal or the logical sta- tus of that signal. The following is a list of all the characters and what they stand for. Example:TAVLL = Time for Address Valid to ALE Low. TLLPL = Time for ALE Low to PSEN Low. (Load Capacitance for port 0, ALE and PSEN = 100 pF; Load Capacitance for all other outputs = 80 pF.) Table 19-1 Table 19-4, and Table 19-6 give the description of each AC symbols. Table 19-3, Table 19-5 and Table 19-7 give for each range the AC parameter. Table 19-2, Table 19-3 and Table 19-8 gives the freque ncy derating formula of the AC parame- ter for each speed range description. To calculate each AC symbols. take the x value in the correponding column (-M or -L) and use this value in the formula. Example: T LLIU for -M and 20 MHz, Standard clock. x = 35 ns T = 50 ns T CCIV = 4T - x = 165 ns

19.4.2 External Program Memory Characteristics

Table 19-2. Symbol Description Symbol Parameter T Oscillator clock period TLHLL ALE pulse width TAVLL Address Valid to ALE TLLAX Address Hold After ALE TLLIV ALE to Valid Instruction In TLLPL ALE to PSEN TPLPH PSEN Pulse Width TPLIV PSEN to Valid Instruction In TPXIX Input Instruction Hold After PSEN TPXIZ Input Instruction FloatAfter PSEN TAVIV Address to Valid Instruction In TPLAZ PSEN Low to Address Float

4113C–8051–01/08 AT8xc51Rx2 Table 19-3. AC Parameters for a Fix Clock Table 19-4. AC Parameters for a Variable Clock Symbol -M -L Units Min Max Min Max T 25 25 ns TLHLL 35 35 ns TAVLL 5 5 ns TLLAX 5 5 ns TLLIV 65 65 ns TLLPL 5 5 ns TPLPH 50 50 ns TPLIV 30 30 ns TPXIX 0 0 ns TPXIZ 10 10 ns TAVIV 80 80 ns TPLAZ 10 10 ns Symbol Type Standard Clock X2 Clock X Parameter for - M Range X Parameter for -L Range Units TLHLL Min 2 T - x T - x 15 15 ns TAVLL Min T - x 0.5 T - x 20 20 ns TLLAX Min T - x 0.5 T - x 20 20 ns TLLIV Max 4 T - x 2 T - x 35 35 ns TLLPL Min T - x 0.5 T - x 15 15 ns TPLPH Min 3 T - x 1.5 T - x 25 25 ns TPLIV Max 3 T - x 1.5 T - x 45 45 ns TPXIX Min x x 0 0 ns TPXIZ Max T - x 0.5 T - x 15 15 ns TAVIV Max 5 T - x 2.5 T - x 45 45 ns TPLAZ Max x x 10 10 ns

4113C–8051–01/08 AT8xc51Rx2

19.4.3 External Program Memory Read Cycle

19.4.4 External Data Memory Characteristics

Table 19-5. Symbol Description TPLIV TPLAZ ALE PSEN PORT 0 PORT 2 A0-A7 A0-A7 INSTR IN INSTR IN INSTR IN ADDRESS OR SFR-P2 ADDRESS A8-A15 ADDRESS A8 - A15

12 T CLCL

TLLDV ALE to Valid Data In TAVDV Address to Valid Data In TLLWL ALE to WR or RD TAVWL Address to WR or RD TQVWX Data Valid to WR Transition TQVWH Data set-up to WR High TWHQX Data Hold After WR TRLAZ RD Low to Address Float TWHLH RD or WR High to ALE high

4113C–8051–01/08 AT8xc51Rx2 Table 19-6. AC Parameters for a Fix Clock Symbol -M -L Units Min Max Min Max TRLRH 125 125 ns TWLWH 125 125 ns TRLDV 95 95 ns TRHDX 0 0 ns TRHDZ 25 25 ns TLLDV 155 155 ns TAVDV 160 160 ns TLLWL 45 105 45 105 ns TAVWL 70 70 ns TQVWX 5 5 ns TQVWH 155 155 ns TWHQX 10 10 ns TRLAZ 0 0 ns TWHLH 5 45 5 45 ns

4113C–8051–01/08 AT8xc51Rx2

19.4.5 External Data Memory Write Cycle

TRLRH Min 6 T - x 3 T - x 25 25 ns TWLWH Min 6 T - x 3 T - x 25 25 ns TRLDV Max 5 T - x 2.5 T - x 30 30 ns TRHDX Min x x 0 0 ns TRHDZ Max 2 T - x T - x 25 25 ns TLLDV Max 8 T - x 4T -x 45 45 ns TAVDV Max 9 T - x 4.5 T - x 65 65 ns TLLWL Min 3 T - x 1.5 T - x 30 30 ns TLLWL Max 3 T + x 1.5 T + x 30 30 ns TAVWL Min 4 T - x 2 T - x 30 30 ns TQVWX Min T - x 0.5 T - x 20 20 ns TQVWH Min 7 T - x 3.5 T - x 20 20 ns TWHQX Min T - x 0.5 T - x 15 15 ns TRLAZ Max x x 0 0 ns TWHLH Min T - x 0.5 T - x 20 20 ns TWHLH Max T + x 0.5 T + x 20 20 ns TQVWH TLLAX ALE PSEN WR PORT 0 PORT 2 A0-A7 DATA OUT ADDRESS OR SFR-P2 TAVWL TLLWL TQVWX ADDRESS A8 - A15 OR SFR P2 TWHQX TWHLH TWLWH

4113C–8051–01/08 AT8xc51Rx2

19.4.6 External Data Memory Read Cycle

19.4.7 Serial Port Timing - Shift Register Mode

Table 19-7. Symbol Description Table 19-8. AC Parameters for a Fix Clock ALE PSEN RD PORT 0 PORT 2 A0-A7 DATA IN ADDRESS OR SFR-P2 TAVWL TLLWL TRLAZ ADDRESS A8-A15 OR SFR P2 TRHDZ TWHLH TRLRH TLLDV TRHDX TLLAX TAVDV Symbol Parameter TXLXL Serial port clock cycle time TQVHX Output data set-up to clock rising edge TXHQX Output data hold after clock rising edge TXHDX Input data hold after clock rising edge TXHDV Clock rising edge to input data valid Symbol -M -L Units Min Max Min Max TXLXL 300 300 ns TQVHX 200 200 ns TXHQX 30 30 ns TXHDX 0 0 ns TXHDV 117 117 ns

4113C–8051–01/08 AT8xc51Rx2 Table 19-9. AC Parameters for a Variable Clock

19.4.8 Shift Register Timing Waveforms

19.4.9 External Clock Drive Waveforms

19.4.10 AC Testing Input/Output Waveforms

AC inputs during testing are driven at V CC - 0.5 for a logic “1” and 0.45V for a logic “0”. T iming measurement are made at V IH min for a logic “1” and V IL max for a logic “0”. Symbol Type Standard Clock X2 Clock X Parameter for - M Range X Parameter for -L Range Units TXLXL Min 12 T 6 T ns TQVHX Min 10 T - x 5 T - x 50 50 ns TXHQX Min 2 T - x T - x 20 20 ns TXHDX Min x x 0 0 ns TXHDV Max 10 T - x 5 T- x 133 133 ns INPUT DATA VALID VALID VALID VALID 0 1 2 3 4 5 6 8 7 ALE CLOCK OUTPUT DATA WRITE to SBUF CLEAR RI TXLXL TQVXH TXHQX TXHDV TXHDX SET TI SET RI INSTRUCTION 0 1 2 3 4 5 6 7 VALID VALID VALID VALID VCC -0.5V 0.45V 0.7V CC 0.2V CC -0.1 TCHCL TCLCX TCLCL TCLCH TCHCX INPUT/OUTPUT 0.2 V CC + 0.9 0.2 V CC - 0.1 VCC -0.5V 0.45V

4113C–8051–01/08 AT8xc51Rx2

19.4.11 Float Waveforms

For timing purposes as port pin is no longer floati ng when a 100 mV changes from load voltage occurs and begins to float when a 100 mV change fro m the loaded V OH /V OL level occurs. I OL /I OH ≥ ± 20 mA.

19.4.12 Clock Waveforms

Valid in normal clock mode. In X2 mode XTAL2 must be changed to XTAL2/2. FLOAT VOH - 0.1 V VOL + 0.1 V VLOAD VLOAD + 0.1 V VLOAD - 0.1 V

4113C–8051–01/08 AT8xc51Rx2 Figure 19-5. Internal Clock Signals This diagram indicates when signals are clocked internally. The time it takes the signals to propagate to the pins, however, ranges from 25 to 125 ns. This propagation delay is dependent on variables such as temperature and pin loading. Propa- gation also varies from output to output and component. Typically though (T A = 25 °C fully loaded) RD and WR propagation delays are approximately 50 ns. The other signals a re typically 85 ns. Propagation delays are incorpor ated in the AC specifications. DATA PCL OUT DATA PCL OUT DATA PCL OUT SAMPLED SAMPLED SAMPLED STATE4 STATE5 STATE6 STATE1 STATE2 STATE3 STATE4 STATE5 P1 P2 P1 P2 P1 P2 P1 P2 P1 P2 P1 P2 P1 P2 P1 P2 FLOAT FLOAT FLOAT THESE SIGNALS ARE NOT ACTIVATED DURING THE EXECUTION OF A MOVX INSTRUCTION INDICATES ADDRESS TRANSITIONS EXTERNAL PROGRAM MEMORY FETCH FLOAT DATA SAMPLED DPL OR Rt OUT INDICATES DPH OR P2 SFR TO PCH TRANSITION PCL OUT (IF PROGRAM MEMORY IS EXTERNAL) PCL OUT (EVEN IF PROGRAM MEMORY IS INTERNAL) PCL OUT (IF PROGRAM MEMORY IS EXTERNAL) OLD DATA NEW DATA P0 PINS SAMPLED P1, P2, P3 PINS SAMPLED P1, P2, P3 PINS SAMPLED P0 PINS SAMPLED RXD SAMPLED INTERNAL CLOCK XTAL2 ALE PSEN P2 (EXT) READ CYCLE WRITE CYCLE RD WR PORT OPERATION MOV PORT SRC MOV DEST P0 MOV DEST PORT (P1. P2. P3) (INCLUDES INTO. INT1. TO T1) SERIAL PORT SHIFT CLOCK TXD (MODE 0) DATA OUT DPL OR Rt OUT INDICATES DPH OR P2 SFR TO PCH TRANSITION RXD SAMPLED

4113C–8051–01/08 AT8xc51Rx2 20. Ordering Information Table 20-1. Ordering Information Part Number Memory Size Supply Voltage Package Temperat ure Range Packing AT80C51RD2-3CSCM Not Recommended Use AT87C51RD12 AT80C51RD2-3CSIM AT80C51RD2-SLSCM AT80C51RD2-SLSIM AT80C51RD2-RLTIM AT80C51RD2-3CSUM AT80C51RD2-SLSUM AT80C51RD2-RLTUM AT80C51RD2-SLSIL AT80C51RD2-RLTIL AT80C51RD2-SLSUL AT80C51RD2-RLTUL

4113C–8051–01/08 AT8xc51Rx2 Part Number Memory Size Supply Voltage Package Temperat ure Range Packing AT83C51RB2xxx-3CSCM 16K bytes PDIL40 Commercial Stick AT83C51RB2xxx-3CSIM PDIL40 Industrial Stick AT83C51RB2xxx-SLSCM PLCC44 Commercial Stick AT83C51RB2xxx-SLSIM PLCC44 Industrial Stick AT83C51RB2xxx-RLTIM VQFP44 Industrial Tray AT83C51RB2xxx-3CSUM PDIL40 Industrial & Green Stick AT83C51RB2xxx-SLSUM PLCC44 Industrial & Green Stick AT83C51RB2xxx-RLTUM VQFP44 Industrial & Green Tray AT83C51RC2xxx-3CSUM PDIL40 Industrial & Green Stick AT83C51RC2xxx-SLSUM PLCC44 Industrial & Green Stick AT83C51RC2xxx-RLTUM VQFP44 Industrial & Green Tray AT83C51RB2xxx-SLSIL PLCC44 Industrial Stick AT83C51RB2xxx-RLTIL VQFP44 Industrial Tray AT83C51RB2xxx-SLSUL PLCC44 Industrial & Green Stick AT83C51RB2xxx-RLTUL VQFP44 Industrial & Green Tray Part Number Memory Size Supply Voltage Package Temperat ure Range Packing AT83C51RC2xxx-3CSCM 32K bytes PDIL40 Commercial Stick AT83C51RC2xxx-3CSIM PDIL40 Industrial Stick AT83C51RC2xxx-SLSCM PLCC44 Commercial Stick AT83C51RC2xxx-SLSIM PLCC44 Industrial Stick AT83C51RC2xxx-RLTIM VQFP44 Industrial Tray AT83C51RC2xxx-RLTIL VQFP44 Industrial Tray AT83C51RC2xxx-SLSIL PLCC44 Industrial Stick AT83C51RC2xxx-RLTUL VQFP44 Industrial & Green Tray AT83C51RC2xxx-SLSUL PLCC44 Industrial & Green Stick Table 20-1. Ordering Information (Continued)

4113C–8051–01/08 AT8xc51Rx2 21. Package Information

21.1 PDIL40

4113C–8051–01/08 AT8xc51Rx2 STANDARD NOTES FOR PLASTIC D.I.L 1/ CONTROLLING DIMENSIONS : INCHES 2/ DIMENSIONING AND TOLERANCING PER ANSI Y 14.5M - 1982. 3/ DIMENSIONS "A./A1" AND L ARE MEASURED WITH THE PACKAGE SEATED IN JEDEC SEATING PLANE GAUGE GS-3. 4/ "D AND E1" DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTUSIONS. MOLD FLASH OR PROTUSIONS SHALL NOT EXCEED .010 INCH (0.25 mm). 5/ "E AND eA" MEASURED WITH THE LEADS CONSTRAINED TO BE PERPENDIC- ULAR TO THE BASE PLANE. 6/ "eB" IS MEASURED AT THE LEAD TIPS WITH THE LEADS INCONSTRAINED. 7/ CORNER LEADS MAY BE CONFIGURED AS SHOWN IN FIGURE 2.

4113C–8051–01/08 AT8xc51Rx2

21.2 PLCC44

4113C–8051–01/08 AT8xc51Rx2 STANDARD NOTES FOR PLCC 1/ CONTROLLING DIMENSIONS : INCHES 2/ DIMENSIONING AND TOLERANCING PER ANSI Y 14.5M - 1982. 3/ "D" AND "E1" DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTUSIONS. MOLD FLASH OR PROTUSIONS SHALL NOT EXCEED 0.20 mm (.008 INCH) PER SIDE.

4113C–8051–01/08 AT8xc51Rx2

21.3 VQFP44

4113C–8051–01/08 AT8xc51Rx2 STANDARD NOTES FOR PQFP/ VQFP / TQFP / DQFP 1/ CONTROLLING DIMENSIONS : INCHES 2/ ALL DIMENSIONING AND TOLERANCING CONFORM TO ANSI Y 14.5M - 1982. 3/ "D1 AND E1" DIMENSIONS DO NOT INCLUDE MOLD PROTUSIONS. MOLD PROTUSIONS SHALL NOT EXCEED 0.25 mm (0.010 INCH). THE TOP PACKAGE BODY SIZE MAY BE SMALLER THAN THE BOTTOM PACKAGE BODY SIZE BY AS MUCH AS 0.15 mm. 4/ DATUM PLANE "H" LOCATED AT MOLD PARTING LINE AND COINCIDENT WITH LEAD, WHERE LEAD EXITS PLASTIC BODY AT BOTTOM OF PARTING LINE. 5/ DATUM "A" AND "D" TO BE DETERMINED AT DATUM PLANE H. 6/ DIMENSION " f " DOES NOT INCLUDE DAMBAR PROTUSION ALLOWABLE DAMBAR PROTUSION SHALL BE 0.08mm/.003" TOTAL IN EXCESS OF THE " f " DIMENSION AT MAXIMUM MATERIAL CONDITION . DAMBAR CANNOT BE LOCATED ON THE LOWER RADIUS OR THE FOOT.

4113C–8051–01/08 AT8xc51Rx2 22. Datasheet Change Log

22.1 Changes from 4113A - 09/02 to 4113B -03/05

1. Added Green product ordering information.

22.2 Changes from 4113B -03/05 to 4113C -01/08

1. Removed AT80C51RD2 product offering Table 20-1 on page 77 . 2. Updated Package Drawings.

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