M25P40
8/40
OPERAT ING FEA TURES
Page P rogramming
To program one dat a byte, t wo i ns tructions 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 tPP).
To spread this overhead, the Page P rogram (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 Eras e
The Page Program (PP) instruction allows bits to
be reset from 1 to 0. Before this can be applied, the
bytes of memo ry need to hav e been erased to a ll
1s (FFh). This can be achieved either a s ector 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 tSE or tBE).
The Erase instruction must be preceded by a Write
Enable (WREN) instruction.
Polling Duri ng a Write, Program or Erase Cycle
A further improveme nt 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 (tW, tPP, tSE, or tBE). The Write In
Progress (WIP) bit is provi ded in the S tatus Regis-
ter so that the application program can monitor its
value, polling it to establish when the previous
Write cycle, Pro gram cycle or Erase cycle is com-
plete.
Active Power, St a nd - by Po wer an d De ep
Power-Down Modes
When Chip Select (S) is Low, the device is en-
abled, and in the Active Power mode.
When Chip Select (S) is High, the device is dis-
abled, but could rema in in t he Active Powe r mode
until all internal cycles have com pleted (Program,
Erase, Write Status Register). The device then
goes in t o the Stand-by Power m ode. T he device
consumption drops to ICC1.
The Deep Power-down mode is entered when the
specific instruction (the Enter Deep Power-down
Mode (DP) instruction) is executed. The device
consump tion drops further to ICC2. T he de vic e re-
mains in this mode until another specific instruc-
tion (the Release from Deep Power-down Mode
and Read Elect ro nic Sig nature (RES) i nstruction)
is executed.
All other instructions are igno red while the device
is in the Deep Power-down mode. This can be
used as an ext ra software protec tio n mecha nism,
when the device is not in active use, to protect the
device from inadvertent Write, Program or Erase
instructions.
Status Reg ister
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 (WI P) bit indicates
whether the memory is busy with a Write Status
Register, Program or Erase cycle.
WE L bi t. The W rite Enable Latch (WEL) bit indi-
cates the status of the int ernal 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 Eras e 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 th e Hardware
Protected mode. In this mode, the non-volatile bits
of the Status Register (SRWD, BP2, BP1, BP0)
become read-only bits.