M25P16 datasheet(33/55 Pages) STMICROELECTRONICS

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M25P16

Instructions

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6.12

Release from Deep Power-down and Read Electronic

Signature (RES)

To take the device out of Deep Power-down mode, the Release from Deep Power-down and

Read Electronic Signature (RES) instruction must be issued. No other instruction must be

issued while the device is in Deep Power-down mode.

The instruction can also be used to read, on Serial Data Output (Q), the old-style 8-bit

Electronic Signature, whose value for the M25P16 is 14h.

Please note that this is not the same as, or even a subset of, the JEDEC 16-bit Electronic

Signature that is read by the Read Identifier (RDID) instruction. The old-style Electronic

Signature is supported for reasons of backward compatibility, only, and should not be used

for new designs. New designs should, instead, make use of the JEDEC 16-bit Electronic

Signature, and the Read Identifier (RDID) instruction.

Except while an Erase, Program or Write Status Register cycle is in progress, the Release

from Deep Power-down and Read Electronic Signature (RES) instruction always provides

access to the old-style 8-bit Electronic Signature of the device, and can be applied even if

the Deep Power-down mode has not been entered.

Any Release from Deep Power-down and Read Electronic Signature (RES) instruction while

an Erase, Program or Write Status Register cycle is in progress, is not decoded, and has no

effect on the cycle that is in progress.

The device is first selected by driving Chip Select (S) Low. The instruction code is followed

by 3 dummy bytes, each bit being latched-in on Serial Data Input (D) during the rising edge

of Serial Clock (C). Then, the old-style 8-bit Electronic Signature, stored in the memory, is

shifted out on Serial Data Output (Q), each bit being shifted out during the falling edge of

Serial Clock (C).

The instruction sequence is shown in Figure 19.

The Release from Deep Power-down and Read Electronic Signature (RES) instruction is

terminated by driving Chip Select (S) High after the Electronic Signature has been read at

least once. Sending additional clock cycles on Serial Clock (C), while Chip Select (S) is

driven Low, cause the Electronic Signature to be output repeatedly.

When Chip Select (S) is driven High, the device is put in the Stand-by Power mode. If the

device was not previously in the Deep Power-down mode, the transition to the Stand-by

Power mode is immediate. If the device was previously in the Deep Power-down mode,

though, the transition to the Stand-by Power mode is delayed by tRES2, and Chip Select (S)

must remain High for at least tRES2(max), as specified in Table 15. Once in the Stand-by

Power mode, the device waits to be selected, so that it can receive, decode and execute

instructions.

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