M95040-DRMF3TP datasheet(18/41 Pages) STMICROELECTRONICS

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Instructions

M95040-A125 M95040-A145

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DocID024225 Rev 6

4.5

Read from Memory Array (READ)

The READ instruction is used to read the content of the memory.

As shown in Figure 9, to send this instruction to the device, Chip Select (S) is first driven

low.

The bits of the instruction byte and address byte are then shifted in, on Serial Data Input (D).

The most significant address bit, A8, is incorporated as bit b3 of the instruction byte, as

shown in Table 5: Instruction set. The address is loaded into an internal address register,

and the byte of data at that address is shifted out, on Serial Data Output (Q).

If Chip Select (S) continues to be driven low, the internal address register is automatically

incremented, and the next byte of data is shifted out. The whole memory can therefore be

read with a single READ instruction.

When the highest address is reached, the address counter rolls over to zero, allowing the

Read cycle to be continued indefinitely.

The Read cycle is terminated by driving Chip Select (S) high at any time when the data bits

are shifted out on Serial Data Output (Q).

The instruction is not accepted, and is not executed, if a Write cycle is currently in progress.

Figure 9. Read from Memory Array (READ) sequence

1. Depending on the memory size, as shown in Table 6, the most significant address bits are Don’t Care.

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