M25PE10, M25PE20
OPERATING FEATURES
Sharing the Overhead of Modifying Data
To write or program one (or more) data Bytes, two
instructions are required: Write Enable (WREN),
which is one Byte, and a Page Write (PW) or Page
Program (PP) sequence, which consists of four
Bytes plus data. This is followed by the internal cy-
–
–
when the designer knows that the page has
already been erased by an earlier Page Erase
(PE) or Sector Erase (SE) instruction. This is
useful, for example, when storing a fast
stream of data, having first performed the
erase cycle when time was available
cle (of duration t
or t ).
when the designer knows that the only
PW
PP
changes involve resetting bits to 0 that are still
set to 1. When this method is possible, it has
the additional advantage of minimising the
number of unnecessary erase operations, and
the extra stress incurred by each page.
To share this overhead, the Page Write (PW) or
Page Program (PP) instruction allows up to 256
Bytes to be programmed (changing bits from 1 to
0) or written (changing bits to 0 or 1) at a time, pro-
vided that they lie in consecutive addresses on the
same page of memory.
For optimized timings, it is recommended to use
the Page Program (PP) instruction to program all
consecutive targeted Bytes in a single sequence
versus using several Page Program (PP) se-
quences with each containing only a few Bytes
(see Page Program (PP) and AC Characteristics
(33MHz operation)).
An Easy Way to Modify Data
The Page Write (PW) instruction provides a con-
venient way of modifying data (up to 256 contigu-
ous Bytes at a time), and simply requires the start
address, and the new data in the instruction se-
quence.
Polling During a Write, Program or Erase Cycle
The Page Write (PW) instruction is entered by
driving Chip Select (S) Low, and then transmitting
the instruction Byte, three address Bytes (A23-A0)
and at least one data Byte, and then driving Chip
Select (S) High. While Chip Select (S) is being
held Low, the data Bytes are written to the data
buffer, starting at the address given in the third ad-
dress Byte (A7-A0). When Chip Select (S) is driv-
en High, the Write cycle starts. The remaining,
unchanged, Bytes of the data buffer are automati-
cally loaded with the values of the corresponding
Bytes of the addressed memory page. The ad-
dressed memory page then automatically put into
an Erase cycle. Finally, the addressed memory
page is programmed with the contents of the data
buffer.
A further improvement in the write, program or
erase time can be achieved by not waiting for the
worst case delay (t , t , t , or t ). The Write
PW PP PE
SE
In Progress (WIP) bit is provided in the Status
Register so that the application program can mon-
itor its value, polling it to establish when the previ-
ous cycle is complete.
Reset
An internal Power-On Reset circuit helps protect
against inadvertent data writes. Addition protec-
tion is provided by driving Reset (Reset) Low dur-
ing the Power-on process, and only driving it High
when V
has reached the correct voltage level,
CC
V
(min).
CC
Active Power, Standby Power and Deep
Power-Down Modes
When Chip Select (S) is Low, the device is select-
ed, and in the Active Power mode.
All of this buffer management is handled internally,
and is transparent to the user. The user is given
the facility of being able to alter the contents of the
memory on a Byte-by-Byte basis.
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). The device then goes in to the
Standby Power mode. The device consumption
For optimized timings, it is recommended to use
the Page Write (PW) instruction to write all con-
secutive targeted Bytes in a single sequence ver-
sus using several Page Write (PW) sequences
with each containing only a few Bytes (see Page
Write (PW) and AC Characteristics (33MHz oper-
ation)).
drops to I
.
CC1
The Deep Power-down mode is entered when the
specific instruction (the Deep Power-down (DP) in-
struction) is executed. The device consumption
A Fast Way to Modify Data
The Page Program (PP) instruction provides a fast
way of modifying data (up to 256 contiguous Bytes
at a time), provided that it only involves resetting
bits to 0 that had previously been set to 1.
drops further to I
. The device remains in this
CC2
mode until the Release from Deep Power-down in-
struction is executed.
All other instructions are ignored while the device
is in the Deep Power-down mode. This can be
used as an extra software protection mechanism,
when the device is not in active use, to protect the
This might be:
–
when the designer is programming the device
for the first time
7/37
STMICROELECTRONICS [ ST ]
