
M45PE40 Operating features
13/49
4.3 A fast wa y 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 bit s to ‘0’ that had
previously been set to ‘1’.
This might be:
●when the designer is programming the device for the first time
●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
●when the designer knows that the only changes involve resetting bits to ‘0’ that are still
set to ‘1’. When this method is possible, it has the additional advantage of minimizing
the number of unnecessary erase operations, and the extra stress incurred by each
page.
F or 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) sequences with each containing only a few bytes (see Section 6.8: Page
program (PP), Tab le 14: AC characteristics (50 MHz operation), and Table 15: AC
characteristics (75 MHz operation, T9HX (0.11 µm) process)).
4.4 Polling during a write, program or erase cycle
A further improv emen t in the write, prog ram or er ase time can be achie v ed b y not waiting f or
the worst case delay (tPW, tPP
, tPE, or tSE). The write in progress (WIP) bit is provided in the
status register so that the application program can monitor its va lue, polling it to establish
when the previous cycle is complete.
4.5 Reset
An internal power on reset circuit helps protect against inadvertent data writes. Addition
protection is provided by driving Reset (Reset) Low during the power-on process, and only
driving it High when VCC has reached the correct voltage level, VCC(min).
4.6 Active power, standby power and deep power-down modes
When Chip Select (S) is Low, the device is selected, and in the active power mode.
When Chip Select (S) is High, the d e vice is deselecte d, b ut could remain in the act iv e powe r
mode until all inte rnal cycles have completed (prog ram, era se, write). The device then goes
in to the standby power mode. The device consumption drops to ICC1.
The deep power-down mode is entere d when t he specif ic instruction (the deep po w er-down
(DP) instruction) is executed. The device consumption drops further to ICC2. The device
remains in this mode until another specific instruction (the release from deep power-down
and read electronic signature (RES) instruction) is executed.
All other instructions are ignored while the de vice is in the deep po wer-do wn mode. This can
be used as an e xtr a sof twa re protectio n mechanism, when the device is not in active use, to
protect the device from inadvertent write, program or erase instructions.