M95040-DRE datasheet(19/39 Pages) STMICROELECTRONICS

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M95040-DRE

Instructions

4.6

Write to Memory Array (WRITE)

The WRITE instruction is used to write new data in the memory.

As shown in Figure 10, to send this instruction to the device, Chip Select (S) is first driven

low. The bits of the instruction byte, address byte, and at least one data byte are then shifted

in (MSB first), on Serial Data Input (D). The instruction is terminated by driving Chip Select

(S) high at a data byte boundary. Figure 10 shows a single byte write.

Figure 10. Byte Write (WRITE) sequence

A Page write is used to write several bytes inside a page, with a single internal Write cycle.

For a Page write, Chip Select (S) has to remain low, as shown in Figure 11, so that the next

data bytes are shifted in. Each time a new data byte is shifted in, the least significant bits of

the internal address counter are incremented. If the address counter exceeds the page

boundary (the page size is 32 bytes), the internal address pointer rolls over to the beginning

of the same page where next data bytes will be written. If more than 16 bytes are received,

only the last 16 bytes are written.

For both Byte write and Page write, the self-timed Write cycle starts from the rising edge of

Chip Select (S), and continues for a period tW (as specified in Table 12).

The instruction is discarded, and is not executed, under the following conditions:

•

if a Write cycle is already in progress

•

if Write Protect (W) is low or if the addressed page is in the area protected by the Block

Protect (BP1 and BP0) bits

•

if one of the conditions defined in Section 3.4.1 is not satisfied

Note:

The self-timed Write cycle tW is internally executed as a sequence of two consecutive

events: [Erase addressed byte(s)], followed by [Program addressed byte(s)]. An erased bit

is read as “0” and a programmed bit is read as “1”.

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