DS1222 Dallas, DS1222 Datasheet

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DS1222

Manufacturer Part Number
DS1222
Description
BankSwitch Chip
Manufacturer
Dallas
Datasheet

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Part Number:
DS1222
Quantity:
200
FEATURES
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.
www.dalsemi.com
Provides bank switching for 16 banks of
memory
Bank switching is software-controlled by a
pattern recognition sequence on four address
inputs
Automatically sets all 16 banks off on
power-up
Bank switching logic allows only one bank on
at a time
Custom recognition patterns are available to
prevent unauthorized access
Full 10% operating range
Low-power CMOS circuitry
Can be used to expand the address range of
microprocessors and decoders
Optional 16-pin SOIC surface mount package
1 of 4
PIN ASSIGNMENT
GND
PIN DESCRIPTION
A
NC
BS1,BS2,
BS3,BS4
V
GND
CEI
CEO
PF
CEI
AW
PFI
See Mech. Drawings
AX
AY
AZ
W
CC
DS1222 14-Pin DIP
I
-A
Z
1
2
3
4
5
6
7
(300-mil)
Section
14
13
12
11
10
9
8
BankSwitch Chip
V
CEO
BS1
BS2
BS3
BS4
NC
CC
- Address Inputs
- Chip Enable Input
- Chip Enable Output
- No Connection
- Bank Select Outputs
- Bank Select Outputs
- Power Fail Input
- +5 Volts
- Ground
GND
DS1222S 16-Pin SOIC
CEI
AW
PFI
NC
AY
See Mech. Drawings
AX
AZ
(300-mil)
Section
1
2
3
4
5
6
7
8
DS1222
16
15
14
13
12
11
10
9
111899
V
CEO
NC
BS1
BS2
BS3
NC
BS4
CC

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DS1222 Summary of contents

Page 1

... Optional 16-pin SOIC surface mount package 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 ...

Page 2

... P switching is achieved by matching a predefined pattern stored within the DS1222 with a 16-bit sequence received on four address inputs. Prior to entering the 16-bit pattern, which sets the bank switch, a read cycle of 1111 on address inputs AW through AZ should be executed to guarantee that pattern entry starts with bit 0 ...

Page 3

... MAX UNITS 10%) CC MAX UNITS +1 MAX UNITS 10%) CC MAX UNITS DS1222 NOTES NOTES NOTES NOTES 2 ...

Page 4

... OUTPUT LOAD Figure 1 TIMING DIAGRAM-ACCESS TO BANK SWITCH DS1222 ...

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