M950X0-W datasheet(23/46 Pages) STMICROELECTRONICS

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M950x0-W M950x0-R M950x0-DF

Instructions

6.6

Write to Memory Array (WRITE)

As shown in Figure 12: Byte Write (WRITE) sequence, 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, on Serial Data input (D). The instruction is terminated by

driving Chip Select (S) high at a byte boundary of the input data. The self-timed Write cycle,

triggered by the rising edge of Chip Select (S), continues for a period tW (as specified in

Table 16: DC characteristics (M950x0-W, device grade 6) to Table 19: AC characteristics

(M950x0-R or M95040-DF, device grade 6)). After this time, the Write in Progress (WIP) bit

is reset to 0.

In the case of Figure 12: Byte Write (WRITE) sequence, Chip Select (S) is driven high after

the eighth bit of the data byte has been latched in, indicating that the instruction is being

used to write a single byte. If, though, Chip Select (S) continues to be driven low, as shown

in Figure 13: Page Write (WRITE) sequence, the next byte of input data is shifted in, so that

more than a single byte, starting from the given address towards the end of the same page,

can be written in a single internal Write cycle. If Chip Select (S) still continues to be driven

low, the next byte of input data is shifted in, and used to overwrite the byte at the start of the

current page.

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

•

if the Write Enable Latch (WEL) bit has not been set to 1 (by executing a Write Enable

instruction just before)

•

if a Write cycle is already in progress

•

if the device has not been deselected, by Chip Select (S) being driven high, at a byte

boundary (after the rising edge of Serial Clock (C) that latches the last data bit, and

before the next rising edge of Serial Clock (C) occurs anywhere on the bus)

•

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

Protect (BP1 and BP0) bits

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”.

Figure 12. Byte Write (WRITE) sequence

1. Depending on the memory size, as shown in Table 7: Address range bits, the most significant address bits

are Don’t Care.

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