M45PE40-VMP6TP datasheet(12/46 Pages) NUMONYX

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Operating features

M45PE40

12/46

Operating features

4.1

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 cycle (of duration tPW or tPP).

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, provided that they lie in consecutive addresses on the same page of memory.

4.2

An easy way to modify data

The Page Write (PW) instruction provides a convenient way of modifying data (up to 256

contiguous bytes at a time), and simply requires the start address, and the new data in the

instruction sequence.

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 address byte

(A7-A0). When Chip Select (S) is driven High, the Write cycle starts. The remaining,

unchanged, bytes of the data buffer are automatically loaded with the values of the

corresponding bytes of the addressed memory page. The addressed memory page then

automatically put into an Erase cycle. Finally, the addressed memory page is programmed

with the contents of the data buffer.

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.

For optimized timings, it is recommended to use the Page Write (PW) instruction to write all

consecutive targeted Bytes in a single sequence versus using several Page Write (PW)

sequences with each containing only a few Bytes (see Page Write (PW) and AC

characteristics (50 MHz operation)).

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