M25P64 datasheet(8/38 Pages) STMICROELECTRONICS

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M25P64

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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 tPP).

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 tSE or tBE).

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

BE) can be achieved by not waiting for the worst

case delay (tW, tPP, tSE, or tBE). 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 ICC1.

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

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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