Conditional Nonvolatile Controller Chip
DS1234
DS1234 Conditional Nonvolatile Controller Chip
FEATURES • Converts CMOS static RAMs into nonvolatile
memories
• ...
Description
DS1234
DS1234 Conditional Nonvolatile Controller Chip
FEATURES Converts CMOS static RAMs into nonvolatile
memories
Software-controlled write inhibit
Software-controlled battery disconnect extends
battery life
Unconditionally write protects when VCC is out of
tolerance
Consumes less than 100 nA of battery current
Power fail signal can be used to interrupt processor on
power failure
Low forward voltage drop on the VCC switch
Optional 16-pin SOIC surface mount package
PIN ASSIGNMENT
VCCO 1
14 VCCI
NC CEI WEI CEO WEO GND
2 3 4 5 6 7
13 VBAT VCCO
1
16 VCCI
12 A3 11 A2 10 A1 9 A0
NC 2 15 VBAT NC 3 14 NC CEI 4 13 A3 WEI 5 12 A2 CEO 6 11 A1 WEO 7 10 A0
8 PF
GND
8
9 PF
DS1234 14-Pin DIP (300 MIL) DS1234S 16-Pin SOIC (300 MIL)
PIN DESCRIPTION
VCCO NC
– RAM Supply – No Connection
CEI – Chip Enable Input
WEI – Write Enable Input
CEO
– Chip Enable Output to RAM
WEO
– Write Enable Output to RAM
GND
– Ground
PF – Power Fail Output
A0-A3
– Address Inputs
VBAT VCCI
– Battery Input – +5V Supply
DESCRIPTION The DS1234 is a CMOS circuit that converts CMOS RAM into nonvolatile memory and adds two software selectable switches. Incoming power is monitored for an out-of-tolerance condition. When such a condition is detected, chip enable and write enable to the RAM are inhibited to accomplish write protection, and the battery is switched on to supply the memory with uninterrupted power. The two software selectable switches provided by the DS1234 are ca...
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