DS1222
BankSwitch Chip
www.dalsemi.com
FEATURES
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
鹵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
PIN ASSIGNMENT
CEI
PFI
AW
AX
AY
AZ
GND
1
2
3
4
5
6
7
14
13
12
11
10
9
8
V
CC
CEO
BS1
BS2
BS3
BS4
NC
CEI
NC
PFI
AW
AX
AY
AZ
GND
1
2
3
4
5
6
7
8
16
15
14
13
12
11
10
9
V
CC
CEO
NC
BS1
BS2
BS3
NC
BS4
DS1222 14-Pin DIP
(300-mil)
See Mech. Drawings
Section
DS1222S 16-Pin SOIC
(300-mil)
See Mech. Drawings
Section
PIN DESCRIPTION
A
W
-A
Z
CEI
CEO
NC
BS1,BS2,
BS3,BS4
PFI
V
CC
GND
- Address Inputs
- Chip Enable Input
- Chip Enable Output
- No Connection
- Bank Select Outputs
- Bank Select Outputs
- Power Fail Input
- +5 Volts
- 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.
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