X25644 Datasheet, PDF (5/15 Pages) Xicor Inc. – Programmable Watchdog Timer w/Serial E 2 PROM

X25644/46
X25324/26
X25164/66
For the Page Write Operation (byte or page write) to be
completed, CS can only be brought HIGH after bit 0 of the
last data byte to be written is clocked in. If it is brought
HIGH at any other time, the write operation will not be
completed (Figure 4).
To write to the Status Register, the WRSR instruction is
followed by the data to be written (Figure 5). Data bits 0
and 1 must be “0” .
While the write is in progress following a Status Register
or E²PROM Sequence, the Status Register may be read
to check the WIP bit. During this time the WIP bit will be
high.
RESET/RESET Operation
The RESET (X25xx4) output is designed to go LOW
whenever the Watchdog timer has reached its program-
mable time-out limit.
The RESET (X25xx6) output is designed to go HIGH
whenever the watchdog timer has reached its program-
mable time-out limit.
The RESET/RESET output is an open drain output and
requires a pull up resistor.
Operational Notes
The device powers-up in the following state:
• The device is in the low power standby state.
• A HIGH to LOW transition on CS is required to enter an
active state and receive an instruction.
• SO pin is high impedance.
• The Write Enable Latch is reset.
• The Flag Bit is reset.
• Reset Signal is active for t_PURST
Data Protection
The following circuitry has been included to prevent inad-
vertent writes:
• A WREN instruction must be issued to set the Write
Enable Latch.
• CS must come HIGH at the proper clock count in order
to start a nonvolatile write cycle.
Figure 1. Read E²PROM Array Sequence
CS
SCK
0 1 2 3 4 5 6 7 8 9 10
20 21 22 23 24 25 26 27 28 29 30
INSTRUCTION
SI
HIGH IMPEDANCE
SO
16 BIT ADDRESS
15 14 13
3210
DATA OUT
7 654321 0
MSB
7029 FRM 03
5