M95M01-RMW6TP datasheet(25/39 Pages) STMICROELECTRONICS

25 / 39 page

M95M01-R

Instructions

25/39

6.6

Write to Memory Array (WRITE)

As shown in Figure 12, 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. In the case of Figure 12, this occurs after the eighth bit of the data byte has been

latched in, indicating that the instruction is being used to write a single byte. The self-timed

Write cycle starts, and continues for a period tWC (as specified in Table 13), at the end of

which the Write in Progress (WIP) bit is reset to 0.

If, though, Chip Select (S) continues to be driven Low, as shown in Figure 13, 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. The self-

timed Write cycle starts, and continues, for a period tWC (as specified in Table 13), at the

end of which the Write in Progress (WIP) bit is reset to 0.

Each time a new data byte is shifted in, the least significant bits of the internal address

counter are incremented. If the number of data bytes sent to the device exceeds the page

boundary, the internal address counter rolls over to the beginning of the page, and the

previous data there are overwritten with the incoming data. (The page size is 256 bytes).

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 eighth bit, b0, of the last data byte that has been latched in)

●

if the addressed page is in the region protected by the Block Protect (BP1 and BP0)

bits.

Figure 12.

Byte Write (WRITE) sequence

As shown in Table 6, the most significant address bits are Don’t Care.

AI13879

3456789 10

28 29 30 31 32 33 34 35

14 13

3210

36 37 38

High Impedance

Instruction

24-bit address

765432

Data byte

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