X20C17
AUTOSTORE Feature
The AUTOSTORE feature automatically saves the con-
tents of the X20C17’s static RAM to the on-board bit-for-
bit shadow E
2
PROM at power-down. This circuitry in-
sures that no data is lost during accidental power-downs
or general system crashes, and is ideal for microproces-
sor caching systems, embedded software systems, and
general system back-up memory.
The X20C17 automatically initiates a nonvolatile store
cycle whenever Vcc falls below the AUTOSTORE thresh-
old voltage (V
ASTH
). V
CC
must remain above the
AUTOSTORE Cycle End Voltage (V
ASEND
) for the dura-
tion of the store cycle (t
ASTO
). The detailed timing for this
feature is illustrated in the AUTOSTORE timing dia-
gram, below. Once the AUTOSTORE cycle is initiated,
all other device functions are inhibited.
AUTOSTORE CYCLE Timing Diagram and Suggested AUTOSTORE Implementation Circuit
V
CC
5
VOLTS (V)
VCC
AUTOSTORE CYCLE IN PROGRESS
VASTH
VASEND
4
3
2
1
V
CC
tASTO
STORE TIME
X20C17
22µF
TIME (ms)
2015 ILL F30.4
2015 FHD F14
AUTOSTORE CYCLE LIMITS
X20C17
Symbol
t
ASTO (5)
V
ASTH
V
ASEND (5)
Note:
Parameter
AUTOSTORE Cycle Time
AUTOSTORE Threshold Voltage
AUTOSTORE Cycle End Voltage
Min.
4.0
3.5
Max.
2.5
4.3
Units
ms
V
V
2015 PGM T15
(5) t
ASTO
and V
ASEND
are periodically sampled and not 100% tested.
8
XICOR [ XICOR INC. ]
