DS1222 MAXIM | Alldatasheet
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Technical content
FEATURES
/elevenoclock Provides bank switching for 16 banks of memory /elevenoclock Bank switching is software-controlled by a pattern recognition sequence on four address inputs /elevenoclock Automatically sets all 16 banks off on power-up /elevenoclock Bank switching logic allows only one bank on at a time /elevenoclock Custom recognition patterns are available to prevent unauthorized access /elevenoclock Full ±10% operating range /elevenoclock Low-power CMOS circuitry /elevenoclock Can be used to expand the address range of /elevenoclock microprocessors and decoders /elevenoclock Optional 16-pin SOIC surface mount package PIN ASSIGNMENT PIN DESCRIPTION AW-AZ - Address Inputs CEI - Chip Enable Input CEO - Chip Enable Output NC - No Connection BS1,BS2, - Bank Select Outputs BS3,BS4 - Bank Select Outputs IPF - Power Fail Input VCC - +5 Volts GND - Ground
DESCRIPTION
The DS1222 BankSwitch Chip is a CMOS circuit designed to select one of 16 memory banks under software control. Memory bank switching allows for an increase in memory capacity without additional address lines. Continuous blocks of memory are enabled by selecting proper memory bank through a pattern recognition sequence on four address inputs. Custom patterns from Dallas Semiconductor can provide security through uniqueness and prevent unauthorized access. By combining the DS1222 with the DS1212 Nonvolatile Controller x16 Chip, up to 16 banks of static RAMs can be selected. DS1222 BankSwitch Chip www.dalsemi.com DS1222 14-Pin DIP (300-mil) See Mech. Drawings Section CEI VCC AW AY GND CEO BS1 BS2 BS3 BS4 NC PFI AX AZ VCC CEO NC BS1 BS2 BS3 NC BS4 CEI NC PFI AW AX AY AZ GND DS1222S 16-Pin SOIC (300-mil) See Mech. Drawings Section
Initially, on power-up all four bank select outputs are low and the chip enable output ( CEO ) is held high. Table 1. The last five cycles must match the exact bit pattern as shown for addresses AX, AY, and AZ. However, address line AW defines the bank number to be enabled as per Table 2.
ABSOLUTE MAXIMUM RATINGS* Voltage on any Pin Relative to Ground -0.3V to +7.0V Operating Temperature 0 °C to 70°C Storage Temperature -55 °C to +125°C ∗ This is a stress rating only and functional operation of the device at these or any other conditions above those indicated in the operation sections of this specification is not implied. Exposure to absolute maximum rating conditions for extended periods of time may affect reliability. RECOMMENDED DC OPERATING CONDITIONS (0°C to 70°C) PARAMETER SYMBOL MIN TYP MAX UNITS NOTES Power Supply Voltage V CC 4.5 5.0 5.5 V 1 Logic 1 V IH 2.2 V CC +0.3 V 1 Logic 0 V IL -0.3 +0.8 V 1 DC ELECTRICAL CHARACTERISTICS (0°C to 70°C; VCC = 5V ±10%) PARAMETER SYMBOL MIN TYP MAX UNITS NOTES Input Leakage Current I IL -1.0 +1.0 µA I/O Leakage Current I LO -1.0 +1.0 µA Output Current @ 2.4V I OH -1.0 mA 2 Output Current @ 0.4V I OL +4.0 mA 2 Operating Current I CC 15 mA CAPACITANCE (TA = 25°C) PARAMETER SYMBOL MIN TYP MAX UNITS NOTES Input Capacitance C IN 51 0 p F Input/Output Capacitance C I/O 51 0 p F AC ELECTRICAL CHARACTERISTICS (0°C to 70°C; VCC = 5V ±10%) PARAMETER SYMBOL MIN TYP MAX UNITS NOTES Address Setup t AS 5n s Address Hold t AH 50 ns Read Recovery t RR 40 ns Propagation Delay t PD 15 ns 2 Power Fail Input to First CEI tPF 50 ns Chip Enable Low t CW 110 ns NOTES: 1. All voltages are referenced to ground. 2. Measured with a load as shown in Figure 1.
TIMING DIAGRAM-ACCESS TO BANK SWITCH