M25P64
OPERATING FEATURES
Page Programming
To program one data byte, two instructions are re-
quired: Write Enable (WREN), which is one byte,
and a Page Program (PP) sequence, which con-
sists of four bytes plus data. This is followed by the
internal Program cycle (of duration t
PP
).
To spread this overhead, the Page Program (PP)
instruction allows up to 256 bytes to be pro-
grammed at a time (changing bits from 1 to 0), pro-
vided that they lie in consecutive addresses on the
same page of memory.
Sector Erase and Bulk Erase
The Page Program (PP) instruction allows bits to
be reset from 1 to 0. Before this can be applied, the
bytes of memory need to have been erased to all
1s (FFh). This can be achieved either a sector at a
time, using the Sector Erase (SE) instruction, or
throughout the entire memory, using the Bulk
Erase (BE) instruction. This starts an internal
Erase cycle (of duration t
SE
or t
BE
).
The Erase instruction must be preceded by a Write
Enable (WREN) instruction.
Polling During a Write, Program or Erase Cycle
A further improvement in the time to Write Status
Register (WRSR), Program (PP) or Erase (SE or
BE) can be achieved by not waiting for the worst
case delay (t
W
, t
PP
, t
SE
, or t
BE
). The Write In
Progress (WIP) bit is provided in the Status Regis-
ter so that the application program can monitor its
value, polling it to establish when the previous
Write cycle, Program cycle or Erase cycle is com-
plete.
Active Power and Standby Power Modes
When Chip Select (S) is Low, the device is select-
ed, and in the Active Power mode.
When Chip Select (S) is High, the device is dese-
lected, but could remain in the Active Power mode
until all internal cycles have completed (Program,
Erase, Write Status Register). The device then
goes in to the Standby Power mode. The device
consumption drops to I
CC1
.
Status Register
The Status Register contains a number of status
and control bits that can be read or set (as appro-
priate) by specific instructions.
WIP bit.
The Write In Progress (WIP) bit indicates
whether the memory is busy with a Write Status
Register, Program or Erase cycle.
WEL bit.
The Write Enable Latch (WEL) bit indi-
cates the status of the internal Write Enable Latch.
BP2, BP1, BP0 bits.
The Block Protect (BP2,
BP1, BP0) bits are non-volatile. They define the
size of the area to be software protected against
Program and Erase instructions.
SRWD bit.
The Status Register Write Disable
(SRWD) bit is operated in conjunction with the
Write Protect (W) signal. The Status Register
Write Disable (SRWD) bit and Write Protect (W)
signal allow the device to be put in the Hardware
Protected mode. In this mode, the non-volatile bits
of the Status Register (SRWD, BP2, BP1, BP0)
become read-only bits.
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STMICROELECTRONICS [ STMICROELECTRONICS ]
