Figure 9. Write Disable (WRDI) Sequence
M95040, M95020, M95010
S
01234567
C
Instruction
D
High Impedance
Q
AI03790D
Write Disable (WRDI)
One way of resetting the Write Enable Latch
(WEL) bit is to send a Write Disable instruction to
the device.
As shown in Figure 9, to send this instruction to the
device, Chip Select (S) is driven Low, and the bits
of the instruction byte are shifted in, on Serial Data
Input (D).
The device then enters a wait state. It waits for a
the device to be deselected, by Chip Select (S) be-
ing driven High.
The Write Enable Latch (WEL) bit, in fact, be-
comes reset by any of the following events:
– Power-up
– WRDI instruction execution
– WRSR instruction completion
– WRITE instruction completion
– Write Protect (W) line being held Low.
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