CS62180

CS62180 CIRRUS | Alldatasheet

Document overview

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Technical content

Features

• Monolithic T1 Framing Device
• CS62180B Supports SF(D4®), T1DM, ESF and SLC-96® Framing Formats
• CS62180B Contains Updated AIS and Carrier Loss Detection Criteria
• CS62180B is Pin Compatible with DS2180A, and DS2180 General Description The CS62180B is a monolithic CMOS device which encodes and decodes T1 framing formats. The device supports bit-seven and B8ZS zero suppres- sion, and bit-robbed signaling. Clear channel mode can be selected on a per channel basis. The serial interface has been enhanced to allow the CS62180B to share a chip select signal and register address space with the CS61535A, CS61574A, and CS61575 Line Interface Units.

Applications

• T1 Line Cards
• ISDN Primary Rate Line Cards Ordering Information: CS62180B-IL

44 Pin PLCC

-40 to 85 °C DEC '03 DS225PP2 Cirrus Logic, Inc. www.cirrus.com T1 Framer CS62180B Serial Interface Registers Control VDD VSS TEST TSER TABCD TSIGSEL TMO TCHCLK TSIGFR TPOS TNEG TMSYNC TFSYNC Transmit Timing Data Selector F-Bit Data Yellow Alarm Bipolar Coder Transmitter Data DeMUX Synchronizer RLOS RBV RCL RPOS RNEG RFER RCLK RMSYNC RFSYNC Code Gen. Receive Sync Controller CRC Receiver Receive Timing Bipolar Decoder SCLK SDI SDO SPS RSER RABCD RLINK RLCLK RSIGFR RSIGSEL RCHCLK TCLK TLCLK TLINK CS INT RST Alarm Detect RYEL RBL (CS2180B-IL only) CRC Copyright  Cirrus Logic, Inc 2003 (All Rights Reserved)

(Referenced to GND) VDD 6.0 V Input voltage, any pin (Referenced to GND) VIN -1.0 V Input Current, any pin (Note 1) IIN -10 +10 mA Ambient Operating Temperature TA -40 Storage Temperature TSTG -65 150 Soldering Temperature for 10 s. 260 Notes: 1. Transient current of up to 100 mA will not cause SCR latch-up. WARNING: Operation at or beyond these limits may result in permanent damage to the device. Normal operation is not guaranteed at these extremes. RECOMMENDED OPERATING CONDITIONS Parameter Symbol Min Typ Max Units DC Voltage VDD 4.5 5.0 5.5 V Supply Current (Notes 2 and 3) IDD mA Ambient Operating Temperature TA -40 Power Consumption (Notes 2 and 3) PC mW 3. Outputs open. DIGITAL CHARACTERISTICS (TA = -40 to 85 °C; VDD = 5.0 V ±10%; GND = 0 V) Parameter Symbol Min Typ Max Units High-Level Input Voltage (Note 4) VIH 2.0 VDD +0.3 V Low-Level Input Voltage HIL -0.3 +0.8 V High-level Output Voltage (Note 5) VOH VDD - 1.0 V Low-Level Output Voltage (IOUT = 1.6 mA) VOL 0.4 V Output Current @ 2.4 V (Note 6) IOH mA Output Current @ 0.4 V (Note 7) IOL mA Input Leakage Current IIL µA Output Leakage Current (Note 8) ILO µA Input Capacitance CIN pF Output Capacitance COUT pF 5. IOUT = -100 µA. This guarantees the ability to drive one TTL load (VOH = 2.4 V @ IOUT = -40 µA). 6. All outputs except INT, which is open drain. 7. All outputs. 8. Applies to SDO when tristated. CS62180B DS225PP2

t CDV t CDH2 t Serial Port Read Timing 13. Serial port write must precede a port read to provide address information. 14. SDO will go High-Z: 1) if CS returns high at anytime; 2) after outputing MSB. SCLK SDI LSB LSB MSB Control Byte Data Byte DC t CC t CH t CDH1 t CL t CDH1 t CCH t CWH t CS Serial Port Write Timing 11. In the CS62180B, data is latched on the rising edge of SCLK. 12. Shaded regions indicate don’t care states. SWITCHING CHARACTERISTICS - SERIAL PORT (TA = -40 to 85 °C; VDD = 5V ± 10%; VIH = 2.0V; VIL = 0.8V; Maximum input rise & fall times of 10 ns) Parameter Symbol Min Typ Max Units SDI to SCLK Setup tDC ns SCLK to SDI Hold tCDH1 ns SCLK Low Time tCL 250 ns SCLK High Time tCH 250 ns SCLK Rise & Fall Times (Note 9) tR, tF 500 ns CS to SCLK Set up tCC ns SCLK to CS Hold tCCH ns CS Inactive Time tCWH 250 ns SCLK to SDO Valid (Note 9) tCDV 200 ns SCLK Rising to MSB of SDO Hold (Note 10) tCDH2 ns CS to SDO High-Z tCDZ ns Notes: 9. Output load capacitance = 100 pF. 10. SDO goes High-Z after rising edge of SCLK for MSB, regardless of the state of CS. CS62180B DS225PP2

Notes:15. Average reframe time is the time from the rising edge of RLOS until the rising edge of RMSYNC which updates the receiver output timing. 16. With error free data. SWITCHING CHARACTERISTICS - TRANSMITTER (TA = -40 to 85 °C; VDD = 5V ± 10%; VIH = 2.0V; VIL = 0.8V; Maximum input rise & fall times of 10 ns) Parameter Symbol Min Typ Max Units TCLK Period tP 250 648 ns TCLK Pulse Width tWL, tWH 125 324 ns TCLK Rise & Fall Times tF, tR ns TSER, TABCD, TLINK Setup to TCLK Falling tSTD ns TSER, TABCD, TLINK Hold from TCLK Falling tHTD ns TFSYNC, TMSYNC Setup to TCLK Rising tSTS -125 125 ns TFSYNC, TMSYNC Pulse Width tTSP 100 ns Propagation Delays TFSYNC to TMO, TSIGSEL, TSIGFR, TLCLK tPTS ns TCLK Rising to TCHCLK tPTCH ns SWITCHING CHARACTERISTICS - RECEIVER (TA = -40 to 85 °C; VDD = 5V ± 10%; VIH = 2.0V; VIL = 0.8V; Maximum input rise & fall times of 10 ns) Parameter Symbol Min Typ Max Units Transition Time, All Outputs tTTR ns RCLK Period tP 250 648 ns RCLK Pulse Width tWL, tWH 100 324 ns RCLK Rise & Fall Times tF, tR ns RPOS, RNEG Setup to RCLK Falling tSRD ns RPOS, RNEG Hold to RCLK Falling tHRD ns Minimum RST Pulse Width on System Power Up or Restart tRST µs Propagation Delays RCLK to RMSYNC, RFSYNC,RSIGSEL, RSIGFR, RLCLK, RCHCLK tPRS ns RCLK to RSER, RABCD, RLINK tPRD ns RCLK to RYEL, RCL, RFER, RLOS, RBV tPRA ns Average Reframe Time (Notes 15 and 16) 193S RCR.2 = 0 RCR.2 = 1 tRS 3.75 7.25 ms ms 193E RCR.2 = 0 RCR.2 = 1 tRS 7.5 14.5 ms ms T1DM tRS 750 µs SLC-96® tRS 6.0 ms CS62180B DS225PP2

TMO, TLCLK, TSIGSEL TSIGFR TFSYNC, TMSYNC TSER, TABCE, TLINK TLCLK STD t HTD t WH t WL t P t STS t PTS t TSP t PTCH t Transmitter Timing. Note: TMO, TLCLK, TSIGSEL and TSIGFR are generally coincident with the rising edge of TCLK. 10% 90% tR F t Logic 0 Logic 1 VDD - 1.0 V 0.4 V TTR t Transition Times for All Receiver Outputs. Old Alignment New Alignment RLOS RMSYNC t RS Rise and Fall Times for RCLK & TCLK. Reframe Timing. CS62180B DS225PP2

t WL t P t PRD t RCLK RSER, RABCD SRD t HRD t RST t PRA t RFSYNC, RMSYNC, RSIGSEL, RSIGFR RLCLK, RCHCLK RPOS, RNEG RYEL, RCL, RBV, RFER, RLOS RST (RFSYNC) PRS t tP RLINK Receiver Timing. CS62180B DS225PP2

The CS62180B is a monolithic CMOS circuit that encodes and decodes T1 (1.544 MHz) digi- tal transmission formats for SF(D4®) (193S: 12 frames per superframe), ESF (193E: 24 frames per superframe), SLC-96® DDS® T1DM (T1DM: 12 frames per superframe plus unique channel number 24) framing formats. The CS62180B provides full support for individual clear channels, bit- robbed signaling, alarm detection and generation, zero suppression, and idle channels. An overview of the 193S, 193E, SLC-96® and T1DM framing formats is provided in the Applications Section. The device provides independent transmit and receive sides, with a shared serial controller in- terface for use with a host processor. A hardware mode is also available for operation independent of a host controller. The SLC-96® and T1DM formats can be selected only via the CS62180B serial controller interface. The serial interface provides access to 16 on- chip control and status registers. The control registers are used to configure global parameters such as the framing format and zero suppression mode, as well as transmitter or receiver specific parameters. A hardware interrupt is provided, which can be configured via interrupt mask and status registers to signal any combination of alarm conditions. Transmitter commands include enabling external framing bit, CRC, or S-bit insertion, declaring individual DS0 channels clear and/or idle, and enabling yellow and blue alarm modes in differ- ent formats. The receiver can be configured to replace individual incoming channels with idle or digital milliwatt (µ-LAW) codes, and a large variety of resync options are provided. Bipolar violations, CRC and framing errors are automat- ically counted in another set of registers which can be arbitrarily reset via the serial interface to provide variable saturation points. The Receive Status Register (RSR) provides data on all error and alarm conditions, and in conjunction with the Receive Interrupt Mask Register (RIMR), can be configured to signal an interrupt on INT (SLC96: 72 frames per superframe) and in response to any alarm condition. Note: there are two different naming conventions in practice concerning the numbering of bits within a word. The most common convention in EE and Computer Science is to number the bits as 0 - 7, starting from the LSB. This is the con- vention used throughout this data sheet when referring to register bits. A different convention is used in the telecom literature when referring to the bits in a digital transmission stream. In this case, they are numbered 1 - 8, starting from the MSB. This convention is maintained in this data sheet whenever referring to the bits of a DS0 channel word. CS62180B ENHANCEMENTS Enhancements made in the CS62180B include the following. The SLC-96® and DDS® T1DM framing formats are supported in host mode. The AIS (Blue Code) detection is made compatible with TR-TSY-000191 requirements (unframed all ones), and a received-blue-alarm output pin is added to the PLCC package. The Receive Carrier Loss detection criteria is made compatible with the industry standard requirement of 175 ±75 ze- ros. The receiver line code decoder is now universal. The decoder will automatically decode either AMI or B8ZS. The CS62180B B8ZS con- trol option controls only the transmitter’s encoder. The universal decoder simplifies the provisioning of B8ZS in the network. Lastly, the serial control interface was simplified. When writing data bytes on SDI, it is no longer neces- sary to have SDI valid for both the rising and falling edges of SCLK. Rather, SDI need be sta- ble only on the rising edge of SCLK. CS62180B DS225PP2

(hex) and a burst read is 81 (hex).

1.544 MHz

Figure 3. Interfacing to a Crystal T1 LIU. alarm conditions for generation of hardware interrupt. this 8 bit counter surpasses it’s user definable limit. framing mode, zero suppression, or loopback. algorithm or insertion of digital milliwatt codes. generation, clear or idle channel enable, and external S-bit or CRC insertion. individual DS0 channel. When set, that channel is replaced with an idle code. set, that signaling and B7 zero suppression is disabled for that channel. channel data is replaced with an idle or digital milliwatt code. Table 1. On-Chip Registers

The Common Control Register (CCR) deter- mines global operating characteristics common to both the transmitter and receiver. It currently provides for selection of the framing mode (193S, 193E, SLC-96® or T1DM), the format of yellow alarms, the zero suppression format (B7 or B8ZS), loopback operation, and control of output to RSR.2. See Figure 4a for an overview of the CCR. Loopback CCR.0: LPBK Setting LPBK (CCR.0) to "1" puts the CS62180B into loopback mode. While in loopback, the TPOS/TNEG and TCLK outputs are internally rerouted directly to the RPOS/RNEG and RCLK inputs, while an un- framed, all "1’s" stream is output on the TPOS/TNEG pins. All operating modes, except blue alarm transmission, remain functional dur- ing loopback. Note that enabling loopback will usually invoke an out-of-frame (OOF) error un- til the receiver can resync to the new framing alignment. See the section on the Receive Con- trol Register (RCR) for a description of the resync options available. Zero Suppression CCR.1: B7 CCR.2: B8ZS B7 and B8ZS select the zero suppression mode. Setting B7 (CCR.1) to "1" will enable bit 7 zero substitution. This causes any channel word with all zeros to be transmitted with bit 7 (2nd LSB) forced to a "1". B7 mode only affects the transmitter, the receiver does not decode B7. Note that bit 7 stuffing can be disabled on an individual channel basis for clear channel trans- mission via the Transmit Transparent Registers TTR1 - TTR3 (see description of transmitter which follows). B8ZS coding operates independent of channel boundaries, and is transparent to all other func- tions. When using B8ZS, the final transmission stream is examined before transmission, and any eight consecutive zeros will be replaced with a B8ZS code word before transmission. If B8ZS (CCR.2) is set to a "1", B8ZS zero substitution will be enabled in the transmitter. Independent of the setting of CCR.2, any incoming B8ZS codes will be inter- cepted by the receiver and replaced with 8 zeros before being processed by the rest of the receive side. The receiver is always capable of receving either AMI or B8ZS encoded data. Note: For T1DM, CCR.1 and CCR.2 should be set to a "0" since DDS® equipment assures a 1- in-8 one’s density. (MSB) (LSB) FM1 FRSR2 EYELMD FM YELS B8ZS LPBK See Fig. 4b B8ZS FDL See Fig. 4b Bit 2 Disable

0 Transparent 0

1 B7 Stuffing 1

Figure 4a. Common Control Register (CCR) CS62180B DS225PP2

CCR.3: YELS The CS62180B supports two different yellow alarm formats for 193S framing. Whichever format is selected, it will be used by both the transmit side, for yellow alarm genera- tion, and the receive side, for alarm detection. When using 193S framing, a "0" in YELS (CCR.3) will encode/decode yellow alarms as a "0" in bit 2 (2nd MSB) of all channels. Setting CCR.3 to "1" will cause yellow alarms to be en- coded/decoded as a "1" is the S-bit position of frame 12. Note: For T1DM and SLC-96®, CCR.3 should be set to a "0". Framing Format CCR.4: FM CCR.7: FM1 As shown in Figure 4b, CCR.4 and CCR.7 select the framing format. See the text for the Transmit Control Register (TCR) and Re- ceive Control Register (RCR) for further information on the particular options available for each framing format. Note: Changing the framing mode does not force the receiver to resynchronize. A forced resync should be done to insure correct receiver synchronization after the framing mode is changed. 193E Yellow Alarm Format CCR.5: EYELMD The CS62180B supports two different yellow alarm formats for 193E framing. Whichever format is selected, it will be used by both the transmit side, for yellow alarm genera- tion, and the receive side, for alarm detection. When using 193E framing, a "0" in EYELMD (CCR.5) will encode/decode yellow alarms as a repeating sequence of 00FF (hex) on the 4 kHz facility data link (FDL). If CCR.5 is set, 193E yellow alarms will be handled as a "0" in bit 2 (2nd MSB) of all channels. Control of RSR.2 CCR.6: FRSR2 CCR.6 allows you to change the meaning of D2 in the Receive Status Register (RSR.2). If CCR.6 is clear, RSR.2 will report the detection of B8ZS codes in the received T1 input. If CCR.6 is set to a "1", RSR.2 will be used to signal a Change of Frame Alignment (COFA). A COFA is reported when the last receiver resync resulted in a change of framing or multiframing alignment. Refer to the description of the Receive Status Register for further information. FM1 FM Format Selected 193S (D4) 193E (ESF) SLC-96 T1DM Figure 4b. Framing Format Selection CS62180B DS225PP2

The transmit sides of the CS62180B have three types of inputs, the clock, sync, and data inputs. Control is handled through the serial port in host mode, and through the mode control pins in hardware mode (see the last section for a description of hardware mode op- eration). Input Data None of the data inputs are buffered, so the data at each input must be available at the appropriate time for the CS62180B to multiplex into the output stream. All inputs are sampled on the falling edge of TCLK. The delay from input to output is 10 TCLK cycles. NRZ data for DS0 channels is input on TSER. Framing bits (FT or FPS bits) and CRC data may either be generated internally or supplied by the host system. If this data is to be externally sup- plied, it must be inserted into the DS0 input stream at the appropriate frames and input via TSER. S-bits may be generated internally, or externally provided via TLINK. FDL bits are always pro- vided externally on TLINK. Bit-robbed signaling, when enabled, is always sampled at TABCD. The CS62180B muxes in data from these 3 sources (TSER, TLINK, and TABCD) automatically depending on the trans- mitter configuration. Output Data The completed T1 data stream, ready for line transmission, is output on TPOS/TNEG. For op- eration with a line interface which is transparent to line coding, the output can be set to dual- unipolar format by clearing bit 7 of the Transmit Control Register (TCR.7). TCR.7 should be set to a "1" for operation with a line interface which provides AMI or B8ZS coding. In this configura- tion, the data will be output on TPOS in NRZ format, and TNEG will remain low. When oper- ating in hardware mode, output defaults to the dual-unipolar format. TPOS and TNEG may not be tied together, so an external OR gate is rec- ommended if NRZ output is required while in hardware mode. Frame/Multiframe Synchronization The CS62180B maintain timing for frame and multiframe alignment with internal counters driven by TCLK. The timing signals generated by those counters are output on TCHCLK, TMO, TSIGSEL, TSIGFR, and TLCLK. These counters determine when the CS62180B will insert F-bits and sample external signaling data. The frame and multiframe counters can be reset independently via TMSYNC and TFSYNC. If left to run with- out a sync pulse, the CS62180B will arbitrarily choose a framing alignment. A low to high transition of TMSYNC, occurring near the rising edge of TCLK, resets the CS62180B’s counters to mark the bit-period concurrent with the next falling edge of TCLK as the F-bit of the first frame of a new superframe. All other timing will be set to match the superframe alignment automatically. TMSYNC may be pulsed once at start-up and left low, or left running in sync with superframe timing. A low to high transition of TFSYNC, occurring near the rising edge of TCLK, resets the CS62180B’s counters to mark the bit-period concurrent with the next falling edge of TCLK as the F-bit of a new frame. If TMSYNC is used to set superframe alignment, frame alignment will also be set, and TFSYNC may be tied low. There is, of course, no harm in using both TMSYNC and TFSYNC together, as TFSYNC has no effect on multiframe alignment if it is in sync. If, however, TFSYNC is used out of sync with TMSYNC, the superframe align- CS62180B DS225PP2

TSIGSEL runs at twice the frequency of TMO. for B. See Figure 6 for timing diagram. TSIGSEL runs at twice the frequency of TMO. C. See Figure 7 for timing diagram.

10 TCLK Cycle Delay

Figure 5. Bit Level Transmit Timing (193E, signaling enabled)

Transmitter Control Register (TCR) When in host mode, there are a number of op- tions available for transmitter configuration which can be enabled via the Transmit Control Register (TCR), Transmit Transparent Registers (TTR1 - TTR3), and Transmit Idle Registers (TIR1 - TIR3). Serial read and write operations to access these registers are explained in the Se- rial Interface section above. When operating in hardware mode, all control bits in the TCR de- fault to "0" (except TCR.4, which defaults to "1" to enable bit-robbed signaling), and dynamic control is limited to the mode control pins as de- scribed under hardware mode below. The TCR provides control to enable bit-robbed signaling, external framing bit, CRC, or S-bit in- sertion, and yellow and blue alarm modes. It also provides for two different idle code formats, and selection of bipolar or NRZ output. Figure 10 shows an overview of the Transmit Control Reg- ister. Transmit Yellow Alarm TCR.0: TYEL Setting TYEL (TCR.0) to a "1" causes the CS62180B to automatically generate and transmit a yellow alarm in the appropriate format. In 193S mode the yellow alarm format used will be determined by the set- ting of CCR.3. In 193E mode, the yellow alarm format will be determined by the setting of CCR.5. See Common Control Register, above, for description of the available yellow alarm for- mats for 193S and 193E modes. In SLC-96® mode, the CS62180B does not generate the yel- low alarm code. rather, the user transmits the SLC-96® yellow alarm via the data link. In T1DM mode, the yellow alarm is transmitted in bit 5 of channel 24 (and CCR.3 should be set to a "0"). Clearing TCR.0 disables yellow alarm transmission. Transmit Blue Alarm TCR.1: TBL Setting TBL (TCR.1) to a "1" generates a blue alarm; an unframed sequence of all "1’s". If a framed, all "1’s" signal is required, an FF (hex) idle code may be output on all channels via ap- propriate settings of TCR.3 and the TIR registers (see Transmit Idle Code Select below). Blue alarm (Alarm Indication Signal, or AIS) over- rides all other transmission data, and a blue alarm is automatically output during loopback. Clearing TCR.1 disables blue alarm transmis- sion. 193S, SLC-96® and T1DM S-bit Insertion TCR.2: 193SI TCR.2 is applicable to 193S, SLC-96® and T1DM modes, but not to the 193E mode. In the 193S and T1DM modes, setting 193SI (TCR.2) to a "1" allows the S-bit (all even F- bits) to be externally supplied via TLINK. When TCR.2 is clear, the S-bit will be internally gen- erated. In the SLC-96® mode, setting 193SI (TCR.2) to a "1" allows the S-bit (selected even F-bits) to be externally supplied via TLINK, and the user must input all Fs, spoiler and DL bits. When TCR.2 is clear, the CS62180B generates the SLC-96® spoiler bits and Fs bits, and the user (MSB) (LSB) ODF TFPT TCP RBSE TIS 193SI TBL TYEL Bipolar Internal Internal Disabled 7F (Hex) Internal Normal Normal NRZ External External Enabled FF (Hex) External

1 Blue Alarm 1

Yel. Alarm Figure10. Transmit Control Register (TCR) CS62180B DS225PP2

inputs all other DL bits on TLINK using TLCLK. Note: When using internal S-bit generation (TCR.2 = 0) in conjunction with external FT bit insertion (TCR.6 = 1), the CS62180B will logically ’OR’ the value at TSER with the internally generated value. This means that the data on TSER during S-bit periods should always be "0" to avoid corrupting the generated FS pattern. Transmit Idle Code Select TCR.3: TIS Individual DS0 channels can be replaced with idle codes by setting the corresponding bits in the Transmit Idle Registers (TIR1 - TIR3) de- scribed below. TIS (TCR.3) selects which of two codes to use. A "0" in TCR.3 will cause a 7F (hex) to be inserted into the channels specified in the TIR. Setting TCR.3 to a "1" will select an FF (hex) code. By asserting all 24 channels idle in the TIR, this setting can be used to generate a "framed" blue alarm. Whichever mode is se- lected, bit-robbed signaling will still effect idle channels unless they are programmed clear (see Transmit Transparent Registers, below). Robbed Bit Signaling Enable TCR.4: RBSE A "0" in RBSE (TCR.4) will disable bit-robbed signaling. Setting TCR.4 to a "1" will enable sig- naling in all channels. In this mode, data on TABCD is inserted into the LSB of all DS0 channels during signaling frames. For mixed voice and data transmission, individual DS0 channels can be programmed clear by setting the corresponding bits in the Transmit Transparent Registers (TTR1 - TTR3) described below. CRC Pass-through TCR.5: TCP In 193E framing mode, the CRC bits (F-bit of frames 2, 6, 10, 14, 18, and 22) may be either generated internally, or supplied by the user. Clearing TCP (TCR.5) causes the CS62180B to generate and insert the CRC bits automatically. If TCR.5 is set to a "1", data for the CRC channel may be externally supplied. When using this mode, CRC bits are sampled from TSER, and must be externally multiplexed into the DS0 channel data at the F-bit times of CRC frames. FT/FPS Pass Through TCR.6: TFPT When TFPT (TCR.6) is clear, the framing bits for 193S, T1DM and SLC-96® (FT), or 193E (FPS) are generated internally and automatically inserted into the outgoing data stream. Setting TCR.6 to a "1" allows the framing bits to be ex- ternally provided. When using this mode, framing bits are sampled from TSER, and must be externally multiplexed into the DS0 channel data at the F-bit times of the appropriate frames. See note under TCR.2, above. Output Data Format TCR.7: ODF ODF (TCR.7) allows the format of the output data at TPOS/TNEG to be set to either dual- unipolar or NRZ format. Clearing TCR.7 selects for dual-unipolar format on TPOS/TNEG. Set- ting TCR.7 to a "1" causes data to be output on TPOS in NRZ format, and TNEG is held low. When operating in hardware mode, output de- faults to the dual-unipolar format. TPOS and TNEG may not be tied together, so an external OR gate is recommended if NRZ is required while in hardware mode. CS62180B DS225PP2

TTR register. See Figure 11. robbed bit signaling is enabled (TCR.4 = 1). Figure 12. Transmit Idle Registers (TIR1 - TIR3)

193S, SLC-96 , T1DM TSER 193E TLINK TSER TLINK FT FS TCR.6 F Passthrough T TCR.6 FPS Passthrough 0 = Internal 1 = External 0 = Internal 1 = External TCR.5 CRC Passthrough TCR.2 S-bit Insertion 0 = Internal 1 = External TSER 0 = Internal 1 = External TSER FDL FPS CRC Robbed Bit Signaling & B7 Zero Suppression Idle Code Insertion Yellow Alarm Insertion B8ZS Zero Suppression Blue Alarm or Loopback TPOS/TNEG TLINK FS SLC-96 DL bits Figure 13a. Transmit Insertion Hierarchy: Framing Bits CS62180B DS225PP2

Transparent Channels? TCR.4 Robbed Bit Signaling? CCR.1 B7 Zero Suppression TSER 1 = Idle 0 = Normal FF 1 = Transparent 0 = Normal 1 = Signaling 0 = Disabled 1 = B7 0 = Disabled Idle Code Insertion Robbed Bit Signaling & B& Zero Suppression TIR Idle Channels? TCR.3 Idle Code F-bit Insertion Yellow Alarm Insertion B8ZS Zero Suppression Blue Alarm or Loopback TPOS/TNEG Figure 13b. Transmit Insertion Hierarchy: Idle Codes, Signaling, and B7 CS62180B DS225PP2

CCR.5 Alarm Format 193E CCR.3 Alarm Format 193S CCR.0 Loopback? CCR.2 B8ZS Zero Suppression? TCR.1 Blue Alarm? TSER 1 = Yes 0 = No B8ZS BLUE BLUE FDL TPOS/TNEG B8ZS Zero Suppression Yellow Alarm Insertion F-bit Insertion Blue Alarm Robbed Bit Signaling & B7 Zero Suppresion 1 = Yes 1 = Yes 0 = No 0 = No Loopback Idle Code Insertion TCR.0 Yellow Alarm? 1 = Yes 0 = No 193S 193E T1DM SLC-96 DL TLINK S12 C24 Figure 13c. Transmit Insertion Hierarchy: Alarms, B8ZS, and Loopback CS62180B DS225PP2

The receive sides of the CS62180B have only three inputs: the clock (RCLK), the in- coming signal (RPOS/RNEG), and a reset pin (RST). The receiver determines the framing syn- chronization of the incoming data, and outputs the timing information on the six timing clocks: RLCLK, RCHCLK, RFSYNC, RMSYNC, RSIGFR, and RSIGSEL. Alarms and error condi- tions are recorded in the Receive Status Register, and output in real time on the five status pins: RYEL, RCL, RBV, RFER, and RLOS. The de- coded data is separated into it’s component channel, link, and signaling components and output on RSER, RLINK, and RABCD respectively. When in host mode, the Receive Control Register allows control of the sync algorithm, and insertion of idle or digital milliwatt (µ-LAW) codes into in- dividual DS0 channels. The internal error counters can be accessed, and the Interrupt Mask Register can be programmed to specify the conditions under which a hardware interrupt is generated on INT. When running in hardware mode, receiver status can still be monitored on the status pins; and access to the error counters, sync algorithm, interrupt mask, and the insertion of idle codes are disabled. Input Data The receiver accepts the incoming T1 stream via RPOS/RNEG in dual-unipolar format. Tying RPOS/RNEG together disables the bipolar viola- tion alarm and allows reception of data in NRZ format. Input data is sampled on the falling edge of RCLK. Delay from input at RPOS/RNEG to out- put on RSER is 13 RCLK periods. Output Data The receiver will attempt to sync and decode the framing format selected via CCR.4 and CCR.7. The decoded T1 stream is output in NRZ format on RSER, and updated every RCLK period. Output data is latched on the rising edge of RCLK, and held until the next update. Link and signaling data is always output on RLINK and RABCD respectively, independent of the transmitter configuration. RABCD outputs the LSB of every DS0 channel word, whether it is cur- rently a signaling frame or not. The data is updated on the channel boundary, concurrent with the MSB, and held until the next update (8 or 9 bits). RLINK outputs either S-bit, SLC-96® DL or FDL bits, depending on the framing format. Data is up- dated 1 bit period prior to the FS or FDL frame and held until the next update (2 frames). Output Clocks Several timing clocks are provided for identify- ing this data. The timing clocks are RLCLK, RCHCLK, RFSYNC, RMSYNC, RSIGFR, and RSIGSEL. Logical combination of these six sig- nals allows easy extraction of any part of the received data stream. RMSYNC runs on a 50% duty cycle, and transitions high at the start of each new superframe output on RSER. RFSYNC transitions high at the start of every new frame. Individual DS0 channels are identified by RCHCLK, which runs on a 50% duty cycle and transitions high at the MSB of every individual time slot. Bit level timing is shown in Figure 14. 193S Timing Link data can be identified by RLCLK, which goes high for all odd numbered frames. RSIGFR is high for signaling frames, and low at all other times. RSIGSEL runs at twice the frequency of RMSYNC. Logical combination of RMSYNC and RSIGSEL provides a way to distinguish the 6th and 12th frames for external multiplexing of signaling channels. RMSYNC is high for those frames containing A signaling bits, and low for frames containing B bits. Refer to Figure 15 for a timing diagram. CS62180B DS225PP2

to Figure 19 for an overview of the RCR. that channel in the appropriate RMR register. format) to be inserted into all marked channels. new framing alignment is declared. Figure 20. Receive Mark Registers (RMR1 - RMR3)

0 Ft/FPS only 0

0 Autoresync

Figure 19. Receive Control Register (RCR)

When the receiver initiates an auto resync, RSIGFR is held low, but all other output timing will continue in the old alignment until the new framing is found. When the new framing align- ment is qualified, the output timing will change to the new alignment at the beginning of the next superframe (or at the start of frame 13 in SLC- 96® mode), and RLOS will return low one bit period before the F-bit of the second frame. A receiver resync has no effect on the transmit side timing or configuration, and behavior of the output timing and RLOS pin is the same as that for an auto resync described above. This is in contrast to a reset initiated via the RST pin, which clears all internal registers on the falling edge, including the transmit side registers, resets the output timing while RST is low, and then in- itiates a receiver resync on the rising edge. The time it takes the receiver to resync depends on resync algorithm selected via RCR.2 and RCR.3. The remaining bits in the RCR (1, 6, and 7) determine under what conditions an automatic resync will be initiated. Forced Resync RCR.0: RESYNC RESYNC (RCR.0) can be used to force a re- ceiver resync. Toggling RCR.0 will initiate a resync immediately on the rising edge. It must then be cleared and set again to initiate another resync. Toggling RCR.0 when going into loop- back mode will force the receiver to resync to the new frame alignment immediately. This is faster than waiting for the internal hardware to recognize an out-of-frame (OOF) condition and initiating an automatic resync. Note: A forced resync should be issued after a change in framing mode to insure correct syn- chronization. Auto Resync Conditions RCR.1: SYNCE RCR.6: OOF RCR.7: ARC SYNCE (RCR.1) can be set to a "1" to com- pletely disable automatic resync. If RCR.1 is clear, a resync will automatically be initiated when the conditions specified by RCR.6 and RCR.7 are detected. OOF (RCR.6) specifies how many framing bits (FT or FPS channels only) must be in error be- fore the receiver declares an out-of-frame (OOF) condition. A resync is always initiated (unless disabled) when an OOF is detected. If RCR.6 is clear, an OOF is declared if 2 out of 4 FT or FPS bits are in error. If RCR.6 is set to a one, an OOF is declared if 2 out of 5 framing bits are errored. Note that the setting of RCR.6 also ef- fects the reporting of OOF events to the Receive Status Register (RSR) and Error Count Register (ECR). Refer to the appropriate sections below for details. ARC (RCR.7) declares whether the receiver will initiate a resync on an OOF event only, or resync on both OOF and carrier loss (RCL). If RCR.7 is cleared, the receiver will commence resync upon detection of either an OOF event (as defined by RCR.6 above), or an RCL. If RCR.7 is set, the receiver will only resync in response to an OOF condition. Resync Algorithm RCR.2: SYNCT RCR.3: SYNCC SYNCT (RCR.2) allows you to declare how many bits must be qualified in the framing pat- tern before the receiver declares synchronization. When RCR.2 is clear, 10 consecutive FT or FPS framing bits preceding an RMSYNC rising edge must be qualified. Setting RCR.2 to a "1" re- quires the CS62180B to qualify 24 consecutive FT or FPS bits preceding an RMSYNC CS62180B DS225PP2

rising edge before declaring synchronization. SYNCC (RCR.3) allows you to modify the algo- rithm employed to search for and qualify the framing alignment. There are two different quali- fying conditions available for each framing mode, and the meaning of RCR.3 depends on which framing mode has been selected via CCR.4. 193S Resync When operating with the 193S framing format, RCR.3 selects whether or not the CS62180B will qualify the FS bits during resync. If a non-standard S-bit pattern is being used, clearing RCR.3 will enable the device to first search for the FT framing pattern to find frame alignment, and then only reset multiframe align- ment if the FS pattern can be found. This means that if a valid FS pattern is not found, synchroni- zation will be declared anyway, and the multiframe alignment indicated by RMSYNC may be false. The S-bits output on RLINK can be used to decode framing externally in such ap- plications. When using standard FS signaling, setting RCR.3 to a "1" will cause the device to cross check the FT and FS patterns to find sync, and both patterns must be valid before sync is de- clared. Synchronization will be declared after the number of FT bits selected by RCR.2 separated by valid FS bits have been qualified. Note that in either setting, S-bit format yellow alarms are recognized by the synchronizer if they have been selected by setting CCR.3. 193E Resync Clearing RCR.3 while in 193E mode will cause the CS62180B to use only the FPS framing pattern when looking for a valid framing alignment. If RCR.3 is set, the device will attempt to qualify the CRC bits after a can- didate alignment has been found. If the CRC codes match, then the new alignment will be de- clared, if not, the device will try two more times. If the third CRC code does not qualify, then the device will start a new resync procedure and continue in this manner until a framing align- ment can be verified with the CRC codes. Note that after 24 ms, if there are still multiple candidates for framing alignment, the device will test the CRC codes to eliminate false candidates regardless of the setting of RCR.3. After the framing alignment has been found, it takes about 9 ms for the device to check the CRC codes for the first superframe. If that superframe fails, it takes about 3 ms to check each additional CRC code. SLC-96® Resync When operating with the SLC-96® framing for- mat, the receiver should be programmed for FS/FT cross-coupling (RCR.3=1) and for mini- mum resync time (RCR.2=0). This causes the CS62180B to sync on the 10 valid FT bits seprated by valid Fs bits in frames 65 through 11, and prevents false synchronization to data link and/or spoiler bits. Note: The CS62180B does not check SLC-96® multiframe alignment once synchronization is declared. In applications such as test equipment where the input data framing format may change or the multiframe alignment may change when the frame alignment does not, the datalink proc- essor should check the phase between RSIGSEL and the DL spoiler bits on RLINK and issue a forced resync when multiframe alignment is in- correct. In the SLC-96® applications, a forced resync should be issued after the device is con- figured. Since the CS62180B defaults to the 193S framing mode at power up it may sync to SLC-96® data while in the 193S mode. If this occurs the multiframe alignment may be incor- rect after the CS62180B is programmed for SLC-96® mode even though the frame alignment CS62180B DS225PP2

Each of the eight bits of the RSR (Figure 21) corresponds to an alarm condition. A bit in the RSR is set when the corresponding alarm is de- tected. It will be cleared by a direct read (a burst read will have no effect) of the RSR, unless the alarm condition persists (see Alarm Servicing, below). TCLK is used to clock the internal cir- cuitry which clears RSR after it is directly read; therefore, a 1.544 MHz signal must always be input to TCLK, even for a "receiver-only" appli- cation. The status pins which correspond to many of the RSR bits operate in real time. They go high when the error is detected, and return low either immediately, or as soon as the error condition is cleared. Alarms are reported syn- chronously with the emergence of the offending bits on RSER. See Figure 22, and the corre- sponding alarm description below for further description of status pin timing. Receive Loss of Sync RSR.0: RLOS RLOS (RSR.0) goes high when a receiver resync is in progress. When the receiver is set to auto resync (RCR.1 = 0), the receiver will commence resync when an OOF event or loss of carrier is detected. If in response to an OOF, RLOS transi- tions high synchronously with the output of the offending F-bit on RSER (see RCR.6). If in response to an RCL, RLOS goes high with the 128th ±1 consecutive zero bit. The RLOS pin will return low one bit period prior to the F-bit of the second frame after the new alignment has been declared (timing signals will reset at the start of the new superframe). Re- fer to Receiver Synchronization, above, for more information. Receive Blue Alarm RSR.1: RBL RBL (RSR.1) will transition high when a blue alarm is detected, and is updated at the begin- ning of odd-numbered frames. A blue alarm is reported whenever unframed all ones occurs, as per Bellcore TR-TSY-000191. The algorithm used is to simul- taneously check for an out-of-frame (OOF) condition, and check for 14 or less zeros out of 13,895 bits. All bits, including frame bits, are tested. RBL goes high on a frame boundary. RBL goes low immediately (indicating the termi- nation of the AIS condition) if OOF goes low, or if 15 or more zeros are counted and the number of bit periods is less than or equal to 13,895. RBL is reported on pin 3 of the 44-pin PLCC package. There is no status pin corresponding to RBL on the 40-pin DIP package. B8ZS/COFA Detect RSR.2: B8ZSD B8ZSD (RSR.2) is a multifunction bit. It can be configured either to report the detection of B8ZS codes, or to indicate a change of framing align- ment. This selection is performed through the setting of CCR.6 (see Common Control Register, above). There is no status pin corresponding to RSR.2. If CCR.6 is clear, RSR.2 will go high every time a B8ZS code is detected in the incoming T1 data. This detector remains operational, whether or not B8ZS substitution has been enabled via CCR.2. CS62180B DS225PP2

If CCR.6 is set to a "1", RSR.2 will go high in response to a Change of Frame Alignment (COFA). A COFA is reported when the last re- ceiver resync resulted in a change of frame or multiframe alignment. RSR.2 will go high at the same time the timing signals are reset after a resync. (See Receiver Synchronization, above.) Frame Bit Error RSR.3: FERR FERR (RSR.3) is set whenever a framing bit is in error. 193S Frame Bit Errors: The framing bits for the 193S is the FT channel (odd F-bits). The RFER status pin (pin 38) signals the same FT errors, but in addition, signals FS errors as well. When signaling a frame bit error, RFER will go high simultaneously with the output of the offending F-bit on RSER, and hold for 2 bit periods. 193E Frame Bit Errors: The framing bits for the 193E mode are the FPS channel (F-bits of frames 4, 8, 12, 16, 20, and 24). The RFER status pin (pin 38) signals the same FPS errors, but in addition, signals CRC errors as well. When signaling a frame bit error, RFER will go high simultaneously with the output of the of- fending F-bit on RSER, and hold for 2 bit periods. When signaling a CRC error, RFER will transition high 1/2 bit before the new superframe to indicate a CRC error in the previous super- frame. It goes high on the falling edge of RCLK, and is held for only one period, returning low on the next falling edge of RCLK. SLC-96® Frame Bit Errors: The framing bits for the SLC-96® mode is the FT channel (odd F- bits). The RFER status pin (pin 38) signals the same FT errors, but in addition, signals FS errors as well. The presence of DL bits in FS bit posi- tions will not be reported as frame bit errors on pin RFER, or in registers RSR.3 and ECR.0-3, and will not contribute to determining that an OOF condition exists. When signaling a frame bit error, RFER will go high simultaneously with the output of the offending F-bit on RSER, and hold for two bit periods. T1DM Frame Bit Errors: The framing bits for the T1DM mode are the FT and FS bits, plus the channel 24 sync word. The RFER status pin (pin 38) signals errors in the frame bits. RFER will go high simultaneously with the F-bit of the frame following the frame in which the error(s) occured, and will remain high for two bit peri- ods. Receive Carrier Loss RSR.4: RCL Carrier loss is declared when 128±1 consecutive zero’s are detected at RPOS/RNEG. RCL (RSR.2) and the RCL pin (pin 36) transition high with the output of the 128th±1 zero bit on RSER. The RCL pin will return low as soon as the next "1" is received at RPOS/RNEG. Receive Yellow Alarm RSR.5: RYEL RYEL (RSR.5) transitions high when a yellow alarm is detected. The format of the alarm de- tected is determined by the settings of either CCR.3 or CCR.5, depending on the framing for- mat being used. The RYEL pin (pin 21) will return low as soon as the alarm clears, that is, when the next expected alarm bit no longer indi- cates an alarm. CS62180B DS225PP2

"0" in bit 2 (2nd MSB) of every DS0 channel. detected in a bit 2 position. Count Register (ECR), as shown in Figure 23. event is detected (the 16th or greater). while in 193E mode, the FPS bits are used. ers must be read or written simultaneously. when resync is in progress (RLOS high). counts up from 0 (all "0’s") to 255 (all "1’s"). Figure 23. Error Count Register (ECR)

For stand alone applications or prototyping in which the device is to operate without a host processor, the CS62180B can be configured to run in hardware mode by tying the Serial Port Select pin (SPS) to ground (VSS). This disables the serial port and redefines pins 14-18 (16-20, PLCC) as mode control pins. All registers are cleared, with the exception of the control bits which are mapped to the mode con- trol pins, and TCR.4, which is set to "1", enabling robbed bit signaling. This means that, with the exception of robbed bit signaling, the configuration of the CS62180B in hardware mode is the same as if it were in host mode with all control bits cleared. Dynamic control of a few of the control bits is provided by mapping them directly to pins 14-18 (16-20, PLCC). Operation of these pins is described in Hardware Mode Control Pins and Table 2. Note that the SLC-96® and T1DM framing formats are not supported in the hardware mode. When operating in hardware mode, bit-robbed signaling is enabled for all channels. Signaling data sampled from TABCD is inserted into the 8th bit position (LSB) of every DS0 channel dur- ing signaling frames (every 6th frame). There is no facility for programming individual channels clear, however; all channels may be made trans- parent by tying TABCD to TSER. When pulling 193SI high for external S-bit in- sertion in 193S mode, data is sampled from TLINK and inserted into the F-bits of even frames. The 193SI pin has no effect when the device is in 193E mode. When using 193E for- mat, TLINK is sampled for insertion into every odd F-bit (FDL). CRC data is internally gener- ated and cannot be externally supplied. The receiver will initiate a resync if 2 of the pre- vious 4 framing bits were in error. It will declare synchronization after 10 consecutive F-bits are qualified. When in 193E mode, CRC errors will be reported on RFER, but not used to qualify synchronization. Receiver status can be moni- tored via the status outputs: RYEL, RCL, RBV, RFER, and RLOS. There is no support for gen- erating blue alarms or idle code insertion when in hardware mode. Hardware Mode Control Pins Framing Format The FM pin allows selection of the framing mode for both transmit and receive sides. Hold- ing this pin low selects 193S framing mode. 193E framing may be selected by pulling the FM pin high. PIN NUMBER REGISTER MAPPING

DESCRIPTION

TCR.2 193S: S-bit Insertion 0 = Internal 1 = External CCR.4 Framing Mode Select 0 = 193S 1 = 193E TCR.0 Transmit Yellow Alarm 0 = Disabled 1 = Enabled CCR.1 B7 Zero Suppression 0 = Transparent 1 = B7 Stuffing CCR.2 B8ZS Zero Suppression 0 = Disabled 1 = Enabled Table 2. Hardware Mode Control Pins

A yellow alarm may be generated on the trans- mit side by pulling TYEL high. In 193S mode, bit 2 yellow alarms are supported internally. In 193E mode, FDL yellow alarms are supported. These formats are also detected by the receiver and reported on RYEL. Blue alarms are not sup- ported in hardware mode, except for the transmission of all "1’s" on TPOS/TNEG during loopback. If S-bit yellow alarm is desired while in 193S mode, it may be externally provided via S-bit in- sertion, enabled by pulling the 193SI pin high. There is, however, no way to generate a bit 2 yellow alarm while in 193E mode. Moreover, the device will not decode either of these formats, while in hardware mode. If they are required, ex- ternal alarm detection must be provided. Zero Suppression B7 selects the B7 zero suppres- sion format for the transmitter. Pulling the B7 pin high enables bit 7 stuffing. Pulling the B8ZS pin high enables B8ZS encoding on the transmit- ter. The receiver is always capable of decoding either B8ZS or AMI-encoded data. Transparent mode may be selected by holding both pins low. Loopback Loopback is also provided in the hardware mode by simultaneously driving the B7 and B8ZS pins high. The previous state of the pins is main- tained, and the selected zero suppression mode remains effective during loopback. While in loopback, an unframed all "1’s" signal (Blue alarm) is output on TPOS/TNEG. CS62180B DS225PP2

RECEIVE NEGITAVE BIPOLAR DATA TRANSMIT SIGNALING SELECT TSIGSEL RPOS RECEIVE POSITIVE BIPOLAR DATA TRANSMIT SIGNALING FRAME TSIGFR RST RESET TRANSMIT ABCD SIGNALING TABCD TEST TEST MODE TRANSMIT LINK DATA TLINK RSIGSEL RECEIVE SIGNALING SELECT TRANSMIT LINK CLOCK TLCLK RSIGFR RECEIVE SIGNALING FRAME TRANSMIT POSITIVE BIPOLAR DATA TPOS RABCD RECEIVE ABCD SIGNALING TRANSMIT NEGITIVE BIPOLAR DATA TNEG RMSYNC RECEIVE MULTIFRAME SYNC RECEIVE ALARM INTERRUPT (193SI)INT RSFYNC RECEIVE FRAME SYNC SERIAL DATA IN (FM)SDI RSER RECEIVE SERIAL DATA SERIAL DATA OUT (TYEL)SDO RCHCLK RECEIVE CHANNEL CLOCK CHIP SELECT (B7)CS RCLK RECEIVE CLOCK SERIAL DATA CLOCK (B8ZS)SCLK RLCLK RECEIVE LINK CLOCK SERIAL PORT SELECT SPS RLINK RECEIVE LINK DATA SIGNAL GROUND VSS RYEL RECEIVE YELLOW ALARM TMSYNC TFSYNC VDD RBL (CS62180B PLCC only) RLOS TCLK RFER TCHCLK RBV NC RCL TSER RNEG TMO RPOS TSIGSEL RST TSIGFR TEST TABCD RSIGSEL TLINK RSIGFR TLCLK RABCD TPOS RMSYNC TNEG RFSYNC (193SI) INT RSER (FM) SDI RCHCLK (TYEL) SD0 NC (B7) CS RCLK (B8ZS) SCLK RLCLK SPS NC VSS RLINK RYEL CS62180B-IL CS62180B DS225PP2

VDD - Positive Supply, Pin 40 (PLCC, Pin 44). Positive digital power supply. Nominally +5.0 Volts.VDD current requirements increase if RCLK is static, and if RST is held high. VSS - Signal Ground, Pin 20 (PLCC, Pin 22). Power supply ground. Nominally 0 volts. Host Mode Serial Interface Pins 14 - 18 (PLCC, 16 - 20) are multifunctional. When in Host mode, they operate as serial interface pins. When in hardware mode, they are redefined as mode control pins. Their hard- ware mode operation is described separately under Hardware Mode Control Pins, below. SPS - Serial Port Select, Pin 19 (PLCC, Pin 21). Must be tied to VDD to select host mode, allowing operation of serial port. Tying SPS to VSS selects hardware mode. Selecting hardware mode clears all internal registers except the com- mon control register (CCR) and transmitter control register (TCR), and redefines pins 14 through 18 (PLCC, 16 - 20) as mode control pins. Inputs SDI - Serial Data In, Pin 15 (PLCC, Pin 17). Serial data input for addressing and writing to on-board control registers. Data is input LSB first. Input data is latched on the rising edge of SCLK. CS - Chip Select, Pin 17 (PLCC, Pin 19). CS low enables serial port for read or write. When CS transitions high, all data transfers are terminated, port control logic is disabled, and SDO is tri-stated to allow for multiprocessor interface. SCLK - Serial Data Clock, Pin 18 (PLCC, Pin 20). Used to read or write the serial port. Data at SDO is output on the falling edge of SCLK and held to the next falling edge. Input data on SDI is latched on the rising edge of SCLK. Outputs INT - Receive Alarm Interrupt, Pin 14 (PLCC, Pin 16). Pulled low to flag host controller when an alarm interrupt condition occurs. The user may select which alarm conditions will trigger an interrupt by appropriately setting the Receive Interrupt Mask Register (RIMR). INT is an open drain output, and should be tied to the positive supply (VDD) through a resistor. CS62180B DS225PP2

SDO - Serial Data Out, Pin 16 (PLCC, Pin 18). When reading the serial port, data is output LSB first. Data is updated on the falling edge of SCLK and held to the next falling edge. SDO goes to a high impedance state when CS is high or after the rising edge of SCLK corresponding to the output of the MSB (last bit output). Hardware Mode Control Pins Pins 14 - 18 (PLCC, 16 - 20) are multifunctional. When in Host mode, they operate as serial interface pins. When in hardware mode, they are redefined as mode control pins. Their host mode operation is described separately under Host Mode Serial Interface, above. SPS must be tied low to enable hardware mode. 193SI - 193S S-bit Insertion, Pin 14 (PLCC, Pin 16). In hardware mode, this pin is redefined as a control pin and maps directly to TCR.2. Holding the pin low while in 193S framing format, configures the CS62180B to generate the FS framing pattern internally for transmission. Pulling 193SI high allows external insertion of transmitted S-bits via TLINK. FM - Frame Mode Select, Pin 15 (PLCC, Pin 17). In hardware mode, this pin is redefined as a control pin and maps directly to CCR.4. Holding the FM pin low configures the CS62180B for 193S framing format, pulling it high selects the 193E format. TYEL - Transmit Yellow Alarm, Pin 16 (PLCC, Pin 18). In hardware mode, this pin is redefined as a control pin and maps directly to TCR.0. Pulling the TYEL pin high enables transmission of a yellow alarm in the default format. In 193S mode yellow alarms default to a "0" in bit 2 (D6) of all DS0 channels. In 193E mode, yellow alarms are encoded/decoded as a repeating pattern of 00FF (hex) on the FDL. B7 - Bit 7 Zero Suppression, Pin 17 (PLCC, Pin 19). In hardware mode, this pin is redefined as a control pin and maps directly to CCR.1. Holding the B7 pin low disables bit 7 stuffing (B7) for transparent operation. Pulling the pin high enables B7 zero suppression. Pulling the B7 and B8ZS pins high simultaneously puts the CS62180B into loopback operation. B8ZS - Bipolar Eight Zero Suppression, Pin 18 (PLCC, Pin 20). In hardware mode, this pin is redefined as a control pin and maps directly to CCR.2. On the CS62180B, pulling the B8ZS pin high enables B8ZS zero suppression in just the transmitter, since the CS62180B receiver is always capable of receiving either B8ZS or AMI-encoded data. Pulling the B7 and B8ZS pins high simultaneously puts the CS62180B into loopback operation. CS62180B DS225PP2

TCLK - Transmit Clock, Pin 3 (PLCC, Pin 4). 1.544 MHz primary transmitter clock. Divided down internally to provide timing signals. TPOS and TNEG are updated on the rising edge of TCLK. Input transmission data (TSER, TABCD, and TLINK) is sampled on the falling edge of TCLK. A 1.544 MHz signal must be input into TCLK even for those applications where the transmitter is not being used. TCLK is used by the circuitry which clears status registers after those regis- ters have been directly read (non-burst mode read). TMSYNC - Transmit Multiframe Sync, Pin 1 (PLCC, Pin 1). A low to high transition of TMSYNC, occurring near the rising edge of TCLK, resets transmit- ter’s frame and multiframe counters, identifying bit period (at TSER) concurrent with the next falling edge of TCLK as the F-bit of frame 1. If tied low, TFSYNC may be used to set frame alignment, and the CS62180B will arbitrarily choose multiframe alignment. Internal channel, frame, and multiframe counters are output on TCHCLK, TMO, TSIGSEL, TSIGFR, and TLCLK. TFSYNC - Transmit Frame Sync, Pin 2 (PLCC, Pin 2). A low to high transition of TFSYNC, occurring near the rising edge of TCLK, resets transmit- ter’s frame counters, identifying bit period (at TSER) concurrent with the next falling edge of TCLK as the F-bit of a new frame. If tied low, TMSYNC may be used to set both frame and multiframe alignment. Without any sync input, the CS62180B will arbitrarily choose both frame and multiframe alignment. Internal channel, frame, and multiframe counters are output on TCHCLK, TMO, TSIGSEL, TSIGFR, and TLCLK. TSER - Transmit Serial Data, Pin 5 (PLCC, Pin 7). Input data (NRZ format), sampled on the falling edge of TCLK. TSER may also be used to provide externally supplied data for insertion into FT, FPS, and CRC channels. Refer to Trans- mit Control Register, bits 5 and 6. Delay from TSER to TPOS/TNEG is 10 TCLK periods. TABCD - Transmit ABCD Signaling, Pin 9 (PLCC, Pin 11). When enabled, by setting bit 4 of the Transmit Control Register (TCR), data provided on TABCD is inserted into the 8th bit position (LSB) of every DS0 channel during signaling frames. Those are frames 6 and 12 in 193S format, and 6, 12, 18, and 24 in 193E. Signaling on individual DS0 channels may be suppressed by declaring those channels transparent in the Transmit Transparent Registers (TTR). Signaling in hardware mode is always enabled. Delay from TABCD to TPOS/TNEG is 10 TCLK periods. CS62180B DS225PP2

TLINK - Transmit Link Data, Pin 10 (PLCC, Pin 12). In 193S framing mode, setting bit 2 of the Transmission Control Register (TCR) enables data on TLINK to be inserted into the S-bit channel (F-bit of all even frames). In 193E mode, TLINK is sampled for data to be inserted into the F-bit of all odd frames for the 4 kHz facility data link (FDL). In the SLC-96® mode, TLINK is sampled for data to be inserted into the DL. In T1DM mode, TLINK is sampled for data to be inserted into the channel 24 "A" data link. Delay from TLINK to TPOS/TNEG is 10 TCLK periods. In hardware mode, external S-bit insertion on TLINK is enabled by setting pin 14 (193SI) high. Outputs TPOS, TNEG - Transmit Bipolar Data Outputs, Pins 12 and 13 (PLCC, Pins 14 and 15 ). Coded data for transmission, updated on rising edge of TCLK. If TCR.7 is clear, or the CS62180B is in hardware mode, data is output in dual-unipolar format. If TCR.7 is set to a "1", data is output on TPOS in NRZ format, and TNEG is held low. Delay from input to TPOS/TNEG is 10 TCLK periods. TCHCLK - Transmit Channel Clock, Pin 4 (PLCC, Pin 5). 192 kHz clock which identifies DS0 channel boundaries. TCHCLK rises to indicate that the next bit input on TSER is the first bit (MSB) of the DS0 channel. TCHCLK has a 50% duty cycle. TMO - Transmit Multiframe Out, Pin 6 (PLCC, Pin 8). Output of internal multiframe counter. Rising edge marks beginning of multiframe, with 50% duty cycle. Internal multiframe counter can be set on the rising edge of TMSYNC. In 193S mode, TMO is high for frames 1-6, and low for frames 7-12, allowing easy distinction of signaling channels A and B. In 193E mode, TMO is high for 1-12, and low for 13-24, and can be used together with TSIGSEL to distinguish channels A, B, C, and D. TSIGSEL - Transmit Signaling Select, Pin 7 (PLCC, Pin 9). In 193S, 193E and T1DM modes, TSIGSEL runs at 2x TMO with a 50% duty cycle. Together with TMO, TSIGSEL provides a way to distinguish signaling channels A, B, C, and D in 193E mode. TMO is high for channels A and B. TSIGSEL is high for channels A and C (frames 1-6 and 13-18). In SLC-96® mode, TSIGSEL provides a way to distinquish when the DL bits are to input. TSIGFR - Transmit Signaling Frame, Pin 8 (PLCC, Pin 10). TSIGFR goes high during signaling frames only, remaining low at all other times. Signaling frames are frames 6 and 12 in 193S, SLC-96® and T1DM modes, and 6, 12, 18, and 24 in 193E mode. TLCLK - Transmit Line Clock, Pin 11 (PLCC, Pin 13). In 193S, 193E and SLC-96® modes, TLCLK runs at 4 kHz with a 50% duty cycle. It’s high during odd numbered frames, and is useful for marking FS or FDL channel timing (input on TLINK), and FT, FPS, and CRC channels (input on TSER). In T1DM, TLCLK runs at 8 kHz, with a duty cycle of one bit period high per frame. CS62180B DS225PP2

RCLK - Receive Clock, Pin 24 (PLCC, Pin 27). 1.544 MHz primary receiver clock. Receiver data is output on the rising edge, and input on the falling edge of RCLK. If no signal is present on RCLK, RST should be held low to minimize power consumption. RPOS, RNEG - Receive Bipolar Data Inputs, Pins 34 and 35 (PLCC, Pins 38 and 39). Recovered data, sampled on falling edge of RCLK. Tie pins together to receive NRZ data and disable bipolar violation monitoring circuitry. Delay from RPOS/RNEG to output at RSER is 13 RCLK periods. RST - Reset, Pin 33 (PLCC, Pin 37). Falling edge of RST clears all internal registers and resets receiver error counters. A receiver resync is forced when RST returns high. This resync effects only the receiver synchronization, and has no effect on transmit timing, but transmit control modes are cleared. The host processor should restore all control modes following a reset by writing the appropriate control registers. NOTE: On system power-up, RST must be held low to insure initialization of all on-board registers. Outputs RYEL - Receive Yellow Alarm, Pin 21 (PLCC, Pin 23). Transitions high when a yellow alarm is detected, returns low when yellow alarm is cleared. When in Host mode, Yellow alarm formats for both 193S and 193E modes can be selected via bits 3 and 5 of the Common Control Register. When in hardware mode, the 193S mode defaults to bit 2 Yellow alarms, and the 193E mode defaults to FDL yellow alarms. Refer to bit 5 of the Receive Status Register (RYEL) for a description of alarm detection conditions. RCL - Receive Carrier Loss, Pin 36 (PLCC, Pin 40). On the CS62180B, RCL transitions high if 1281 consecutive "0’s" are detected on RPOS and RNEG and returns low on the next "1". RBL - Receive Blue Alarm, (CS62180B PLCC only, Pin 3). Transitions high on a frame boundary if an unframed-all ones and an out-of-frame condition simultaneously occur. Returns low when either out-of-frame ends or zeros are detected. RBV - Receive Bipolar Violation, Pin 37 (PLCC, Pin 41). If a bipolar violation is detected, RBV goes high simultaneous with output of accused bit on RSER, low otherwise. CS62180B DS225PP2

RFER - Receive Frame Error, Pin 38 (PLCC, Pin 42). Transitions high with the output of an errored framing bit, and is held for 2 bit periods. FT and FS bits are tested in 193S and SLC-96® modes, and FPS bits are tested in 193E. In T1DM mode, the FS, FT and channel 24 sync bits are tested. Also signals CRC errors in 193E mode, by going high 1/2 bit before the next extended superframe, and holding for 1 period (from falling edge of RCLK to next falling edge). RLOS - Receive Loss of Sync, Pin 39 (PLCC, Pin 43). Transitions high during receiver resync, low otherwise. Transitions high when receiver begins a resync, and falls low one frame after new timing is declared. RSER - Receive Serial Data, Pin 26 (PLCC, Pin 30). Received data, output in NRZ format. Data on RSER is valid and stable on the falling edges of RCLK. Delay from RPOS/RNEG to RSER is 13 RCLK periods. RABCD - Receive ABCD Signaling, Pin 29 (PLCC, Pin 33). Signaling data extracted from LSB of DS0 channels during signaling frames is valid on RABCD during corresponding channel output on RSER (LSB is available on RABCD seven bit periods before it appears at RSER). During non-signaling frames, RABCD continues to output LSB concurrently with word on RSER. After update, data on RABCD is valid and stable on the falling edge of RCLK. RLINK - Receive Link Data, Pin 22 (PLCC, Pin 24). In 193S mode, S-bit data is output on RLINK one RCLK prior to start of corresponding even frame, and held for 2 frames until next update. In 193E mode, FDL data is output on RLINK one RCLK prior to start of corresponding odd frame, and held for 2 frames until next update. After update, data on RLINK is valid and stable on the falling edge of RCLK. In SLC-96® mode, all Fs and DL bits are output on RLINK using RLCLK. In T1DM mode, channel 24 "A" link data is output on RLINK, and is valid and stable on the falling edge of RFSYNC. RLCLK - Receive Link Clock, Pin 23 (PLCC, Pin 26). RLCLK runs at 4 kHz with a 50% duty cycle. It’s high during odd numbered frames. RCLK is useful for marking S-bit, DL or FDL channel timing, output on RLINK. RLCLK is present, but serves no useful purpose in the T1DM mode. RCHCLK - Receive Channel Clock, Pin 25 (PLCC, Pin 29). 192 kHz clock which identifies DS0 channel boundaries output on RSER. RCHCLK is useful for parallel to serial conversion of DS0 channel data. RFSYNC - Receive Frame Sync, Pin 27 (PLCC, Pin 31). Goes high for one RCLK period concurrent with the F-bit of each new frame output on RSER, low otherwise. In the T1DM mode, the falling edge of RFSYNC can be used to sample the "A" link channel on RLINK. CS62180B DS225PP2

RMSYNC - Receive Multiframe Sync, Pin 28 (PLCC, Pin 32). Rising edge signals the F-bit of 1st frame of multiframe. RMSYNC runs on 50% duty cycle, high for frames 1-6 in 193S mode, distinguishing signaling channels A and B. In 193E mode, it’s high for frames 1-12, and can be used with RSIGSEL to distinguish channels A, B, C, and RSIGFR - Receive Signaling Frame, Pin 30 (PLCC, Pin 34). High during signaling frames, low at all other times, including resync. Serves no purpose in T1DM mode. RSIGSEL - Receive Signaling Select, Pin 31 (PLCC, Pin 35). In 193E mode, RSIGSEL goes high for frames 1-6 and 13-18, identifying signaling channels A and C. Used together with RMSYNC, which is high for channels A and B, it allows identifica- tion of all 4 signaling channels. In 193S mode, RSIGSEL goes high for frames 1-3 and 7-9. Serves no purpose in T1DM mode. In SLC-96® mode, RSIGSEL goes high in those frames where Fs bits (frames 59 to 11) and the last spolier bit (frame 58) are present; goes low in all other frames (frames 12 to 57). Miscellaneous TEST - Test Mode, Pin 32 (PLCC, Pin 36). Tie to VSS for normal operation. Factory use only. CS62180B DS225PP2

D B A L C 13.72 51.69 1.02 0.36 0.51 3.94 3.18 0.20 2.41 15.24 14.22 52.71 1.65 0.56 1.02 5.08 3.81 0.38 15° 0.540 2.035 0.095 0.040 0.014 0.020 0.155 0.125 0.600 0.008 0.560 2.075 0.065 0.022 0.040 0.200 0.150 0.015 15° 40 pin Plastic DIP 15.87 0.625 D B SEATING PLANE A L C eA 2.67 0.105 NOTES: 1. POSITIONAL TOLERANCE OF LEADS SHALL BE WITHIN 0.25mm (0.010") AT MAXIMUM MATERIAL CONDITION, IN RELATION TO SEATING PLANE AND EACH OTHER. 2. DIMENSION eA TO CENTER OF LEADS WHEN FORMED PARALLEL. 3. DIMENSION E1 DOES NOT INCLUDE MOLD FLASH. NOM 13.97 52.20 1.27 0.46 0.76 4.32 0.25 2.54 NOM 0.550 2.055 0.100 0.050 0.018 0.030 0.170 0.010 eA E D D2/E2 28/44 pin PLCC NO. OF TERMINALS D2/E2 MAX MIN MAX MIN MAX MIN MAX MIN MILLIMETERS MILLIMETERS INCHES INCHES DIM A 4.57 4.20 0.180 0.165 D/E 17.65 17.40 0.685 12.32 12.57 0.485 0.495 B 0.53 0.33 0.021 0.013 e A B e 2.29 0.090 0.695 16.66 16.51 0.650 11.43 11.58 0.450 0.456 0.656 4.57 4.20 0.180 0.165 0.53 0.33 0.021 0.013 2.29 0.090 16.00 14.99 0.590 9.91 10.92 0.390 0.430 0.630 1.19 1.35 0.047 0.053 1.19 1.35 0.047 0.053 NOM 4.45 12.45 0.41 2.79 11.51 10.41 1.27 NOM 0.175 0.490 0.016 0.110 0.453 0.410 0.050 NOM 17.53 16.59 4.45 0.41 2.79 15.50 1.27 NOM 0.690 0.653 0.175 0.016 0.110 0.610 0.050 3.04 0.120 3.04 0.120 D1/E1 CS62180B DS225PP2

T1 is the basic format in the T-carrier PCM transmission system used in the United States. Detailed technical specifications can be found in ANSI T1.107-1988, ANSI T1.403-1993, ANSI T1.408-1990. The T1 format time-division multiplexes 24 dig- itized voice (telephone) or data channels into a single, 1.544 Mbps data stream. This format is used primarily for transmission over dual twisted-pair cable with digital repeaters at 6000 ft. intervals. The T-carrier system also defines higher level formats for long-haul transmission via satellite or microwave relay. These higher level formats are constructed by multiplexing several T1 lines into higher and higher data rates. Figure A2 gives an overview of the T-car- rier hierarchy. Level Number of voice channels Bit Rate (Mbps) T-1 1.544 T-1C 3.152 T-2 6.312 T-3 672 44.736 T-4 4032 274.176 Figure A2. T-carrier Hiearchy Transmit Line Receive Line TV+ RV+ MODE RCLK RPOS RNEG TCLK TPOS TNEG SCLK SDI SDO INT CS +5V RMSYNC RFSYNC RSIGSEL RCHCLK RSER RABCD TMO TSIGSEL TSIGFR TCHCLK TSER TABCD RLCLK RLINK TLCLK TLINK TMSYNC TEST VSS RSIGFR CS62180B CS61535A/74A/75 TFSYNC VDD SPS RCLK RPOS RNEG TCLK TPOS TNEG SCLK SDI SDO INT CS RYEL RCL RBV RFER RLOS RST Data Link Supervision Host Processor TTIP TRING RTIP RRING CLKE

1.544 MHz Serial Backplane

Q Q C D P Q Q C D P RMSYNC RSIGSEL SLC-96 multiframe sync VDD (optional) Backplane Interface Figure A1. Typical System Connection CS62180B DS225PP2

The T1 format provides a 64 kbps channel for each individual voice or data line. These PCM voice channels consist of 8-bit samples which are sampled at 8 kHz for a data rate of 64 kbps. A T1 frame is constructed by multiplexing 24 of these DS-0 channels and inserting a framing bit at the beginning of the series. This results in 192 bits of channel data, plus an F-bit, for a total of

1.544 Mbps (193 bits/frame transmitted at 8

kHz). See Figure A3. Multiple T1 frames are then grouped into super- frames of 12 or 24 frames to provide for framing and signaling synchronization. The older 193S or SF(D4®) format defines a superframe as 12 frames, with the F-bits carrying 2 channels of synchronization signals. The emerging 193E, or Extended Superframe Format (ESF) calls for 24 frames in a superframe. This allows the 24 F-bits to be divided into 3 separate channels for fram- ing, CRC checks, and system messages. Additional variations on T1 are used for Sub- scriber Loop Carrier (SLC-96®) and Digital Data Service (DDS®) T1DM. 193S Framing Format Figure A5 shows the bit uses in the 193S fram- ing format. The framing bits are divided into two channels. The odd F-bits are designated as the FT (terminal framing) channel, which always carries a repeating pattern of "101010". This pat- tern allows synchronization to the frame boundaries, and distinguishes the even and odd frames. The even F-bits are designated as the FS (signaling framing) channel. This channel carries a different synchronization code (001110) which identifies superframe alignment. The FS channel can alternately be used as a message channel for system use, in which case there is no facility provided for multiframe synchronization. Signaling information associated with each indi- vidual voice channel, such as on-hook/off-hook, call progress, dialing digits, etc., is transmitted within the voice channel itself. The signaling data is transmitted in the LSB of each channel Framing bit T1 Frame = 1.544 Mbps CH 24 CH 1 193 bits Channel 1 Channel 24 TDM 8 kHz Sampling 64 kbps each 8 bits f Figure A3. T1 Overveiw

12 Frames = 193S Superframe

Frame 24 (F24) CH 24 CH 1 f Frame 1 (F1) CH 24 CH 1 f Frame 1 (F1) Frame 12 (F12) CH 24 CH 1 f CH 24 CH 1 f

24 Frames = 193E Superframe

Figure A4. Framing Overveiw 193S F-bits Channel bits Signaling Options Frame FT FS Data Signaling T 1-8 1-7 Bit 8 A A 1-8 1-7 Bit 8 A B Figure A5. 193S Framing Format CS62180B DS225PP2

during the 6th and 12th frames. The original LSB of the channel is actually replaced with the sig- naling data, hence this is known as "robbed-bit" signaling. The 6th and 12th frames can be treated as one, 2-state channel, allowing a 2-state signal to be updated twice every superframe. The two frames can also be treated as separate channels (A and B), yielding up to 4 separate codes for each channel every superframe. For voice grade applications, these signaling bits offer no notice- able degradation in the signal quality. When error-free data transmission is required however, robbed bit signaling can be disabled (transparent mode), and some other signaling facility must be provided by the host system. 193E Framing Format The 193E or Extended Superframe Format al- lows much greater flexibility in both the use of the framing bits, and the number of signaling channels provided. As shown in Figure A6, the framing bits are divided into 3 channels. The FPS, or Framing Pattern Sequence, provides a synchronization signal for determining frame and superframe alignment. The FDL, or 4 kHz Facil- ity Data Link, provides a dedicated channel for system messages. The CRC (Cyclic Redundancy Check) channel allows CRC check sums to be transmitted with each superframe to monitor line quality. As with the 193S format, every 6th frame is designated as a signaling frame. The 4 signaling frames (6, 12, 18, and 24) can be mul- tiplexed in different configurations to provide 2, 4, or 16-state signaling codes. SLC-96® Framing Format The SLC-96® T1 format is used between the Lo- cal Digital Switch (LDS) and a SLC-96® Remote Terminal (RT). The framing format is a SF(D4®) superframe format with specialized Data Link (DL) information bits. The DL bits consist of Concentrator (C), Spoiler (S), Mainte- nance (M), Alarm (A) and Protection Line Switch (PLS) bits as shown in Figure A7. T1DM Framing Format The T1DM T1 format is used for DDS® service among hub and local intermediate DDS® offices. As shown in Figure A8, the framing format is a SF(D4®) superframe format with a specialized channel 24 structure. The T1DM accepts up to

23 DS-0 signals and inserts one seven-bit byte

from each signal into the first twenty-three 8-bit channel slots of the DS1 frame. The 24th chan- nel slot contains a special synchronizing byte as shown in Figure A9. DDS® equipment insures that every DS0 channel contains at least one "1". Therefore, neither B8ZS nor bit-7 zero substitu- tion should be selcted in the CS62180B. 193E F-bits Channel bits Signaling Options Frame FPS FDL CRC Data Signaling T m 1-8 m m 1-7 Bit 8 A A A m 1-8 m m 1-7 Bit 8 A B B m 1-8 m m 1-7 Bit 8 A A C m 1-8 m m 1-7 Bit 8 A B D Figure A6. 193E Framing Format CS62180B DS225PP2

Synchronization Pattern = 1 Synchronization Pattern = 0 Synchronization Pattern = 1 Synchronization Pattern = 1 Synchronization Pattern = 1 Yellow Alarm: 0 = alarm; 1 = no alarm 8 kHz Data Link ("A" channel) Synchronization Pattern = 0 Figure A9. T1DM Channel 24 Format SLC-96® F-bits Channel bits SLC-96® F-bits Channel bits Frame FT FS DL Data Signaling Frame FT FS DL Data Signaling 1-8 1-8 S=0 1-7 Bit 8 (A) 1-7 Bit 8 (A) 1-8 1-8 1-7 Bit 8 (B) 1-7 Bit 8 (B) 1-8 1-8 PLS1 PLS2 1-7 Bit 8 (A) PLS3 1-7 Bit 8 (A) 1-8 1-8 PLS4 S=1 1-7 Bit 8 (B) 1-7 Bit 8 (B) 1-8 1-8 C10 1-7 Bit 8 (A) 1-7 Bit 8 (A) 1-8 1-8 C11 S=0 S=1 1-7 Bit 8 (B) 1-7 Bit 8 (B) Figure A7. SLC-96® Framing Format T1DM F-bits Channel Bits Frame FT FS 1-7 (Bit 8 of user channels is reserved for network use) Figure A8. T1DM Framing Format CS62180B DS225PP2

Figure A10 shows a useful overview of the alarm operation in a PCM link. When an intermediate monitoring system (or central office repeater) de- tects a loss of signal, it transmits an all "1’s" signal (Blue alarm, or Alarm Indication Signal) on the line to maintain clock recovery operation in the subsequent digital repeaters and the desti- nation’s receiver. The same Blue alarm may be used by the source transmitter if, for some rea- son, it cannot maintain normal functionality (such as during loopback). When the loss of signal is detected at the inter- mediate monitor, an internal Red alarm (also known as a Service Alarm Indication, or Prompt Maintenance Alarm) is generated. While in a Red alarm mode, the monitor transmits a Yellow alarm back to the source’s receiver, indicating a remote loss of alignment. This Yellow alarm in- forms the source that there’s a problem farther down the line and it’s transmission is not being received at the destination. Zero Substitution As was mentioned in the T1 overview, data is transmitted over dual twisted-pair cable with digital repeaters at 6000 ft. intervals. It is en- coded in a bipolar AMI (Alternate Mark Inversion) format. Successive "1’s" are encoded alternately as positive and negative voltage pulses. A zero is simply an absence of pulses. This means that a long stream of "0’s" is indis- tinguishable from a dead line. Clock recovery circuits in the network maintain clock synchroni- zation by syncing to the "1’s" pulses in the transmission stream. Synchronization may be lost if there are too many consecutive zero’s, hence there is a general requirement that there be at least 12.5 % "1’s" density in the transmission stream. Furthermore, no more than 15 consecu- tive "0’s" are allowable. Various zero substitution schemes have been developed to meet these re- quirements. The CS62180B supports B7 and B8ZS zero suppression formats. B7 Zero Substitution B7 zero substitution guarantees at least one "1" in all DS0 channels. This satasfies the 12.5 % ones density, and guarantees that more than 15 consecutive zeros will never occur. In B7 substi- tution systems, the 7th bit (2nd LSB) of an all zero channel is forced to a "1". This strategy maintains 1’s density in voice grade transmis- sion, with negligible audible interference. The drawback with the B7 format is that it’s impossi- ble for the receiving end to detect and remove the changed bits. This makes B7 zero suppres- sion unacceptable for clear channel transmission, in which the integrity of the data must be main- tained. B8ZS Zero Substitution B8ZS (Bipolar Eight Zero Substitution) satisfies the one’s density requirement without corrupting transmission data. Instead of operating on indi- vidual channels, the B8ZS format looks at the entire transmission stream. Any eight consecutive zeros are replaced with an 8 bit code. This code uses specific bipolar violations of the AMI for- mat to distinguish it from the ordinary data. If the last "1" transmitted before a string of zeros was encoded as a positive pulse, then the B8ZS code for the next eight bits will be 000+-0-+. Similarly, if the last "1" was a negative pulse, then the code will be 000-+0+-. In either case, bipolar violations occur in the fourth and seventh bits. These violations are decoded as a string of Blue Alarm Monitor Loss of Signal = Red Alarm Yellow Alarm Source Transmit Receive Transmit Receive Destination Digital Repeater Yellow Alarm Yellow Alarm Blue Alarm Figure A10. Alarm Operation on a T1 Link. CS62180B DS225PP2

zeros by the CS62180B if B8ZS is enabled. The received B8ZS code is replaced with eight zeros before any other processing is done on the incoming data. Note also that even if B8ZS is not enabled, the CS62180B monitors the incoming signal for B8ZS codes, and reports them on RSR.2 (if CCR.6 = 0). A serious provisioning problem exists in the net- work regarding B8ZS. It is sometimes difficult to selectively turn-on B8ZS on all segments of an end-to-end path through the network, especially when some equipment types, such as M13s, sometimes require that all four lines on a line card be configured the same way. It is thereby highly desireable that all receivers in the network be able to receive B8ZS independent of the pro- visioning of B8ZS on the corresponding transmitter. Therefore, the CS62180B has its B8ZS receiver turned on all of the time, and bit CCR.2 controls only the B8ZS encoder in the transmitter. The CS62180B reports B8ZS occur- rences on RSR.2. B8ZS substitutions will not increment the Bipolar Violation Count register. Digital Milliwatt Code The Digital Milliwatt code is the digital repre- sentation of a 0 dBm0, 1 kHz signal. It’s used as a test reference for calibrating channel bank equipment as specified in AT&T Publication 43801. CS62180B DS225PP2

15 December 2003

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