CAT93CXXXX Datasheet, PDF (9/10 Pages) Catalyst Semiconductor – Supervisory Circuits with Microwire Serial CMOS E2PROM, Precision Reset Controller and Watchdog Timer

Advanced Information
CAT93CXXXX
Erase/Write Enable and Disable
The CAT93CXXXX powers up in the write disable state.
Any writing after power-up or after an EWDS (write
disable) instruction must first be preceded by the EWEN
(write enable) instruction. Once the write instruction is
enabled, it will remain enabled until power to the device
is removed, or the EWDS instruction is sent. The EWDS
instruction can be used to disable all CAT93CXXXX
write and clear instructions, and will prevent any acci-
dental writing or clearing of the device. Data can be read
normally from the device regardless of the write enable/
disable status.
Erase All
Upon receiving an ERAL command, the CS (Chip Se-
lect) pin must be deselected for a minimum of tCSMIN.
The falling edge of CS will start the self clocking clear
cycle of all memory locations in the device. The clocking
of the SK pin is not necessary after the device has
entered the self clocking mode. The ready/busy status
of the CAT93CXXXX can be determined by selecting
the device and polling the DO pin. Once cleared, the
contents of all memory bits return to a logical “1” state.
Write All
Upon receiving a WRAL command and data, the CS
(Chip Select) pin must be deselected for a minimum of
tCSMIN. The falling edge of CS will start the self clocking
data write to all memory locations in the device. The
clocking of the SK pin is not necessary after the device
has entered the self clocking mode. The ready/busystatus
of the CAT93CXXXXcan be determined by selecting the
device and polling the DO pin. It is not necessary for all
memory locations to be cleared before the WRAL com-
mand is executed.
Figure 6. EWEN/EWDS Instruction Timing
SK
CS
STANDBY
DI
1
00
*
* ENABLE=11
DISABLE=00
Figure 7. ERAL Instruction Timing
SK
CS
DI
1
00
10
HIGH-Z
DO
STATUS VERIFY
tCS
STANDBY
tSV
BUSY
tEW
READY
tHZ
HIGH-Z
9-93
Stock No. 21084-01 2/98