M25P40
Instructions
6.12
Release from Deep Power-down and Read Electronic
Signature (RES)
Once the device has entered the Deep Power-down mode, all instructions are ignored
except the Release from Deep Power-down and Read Electronic Signature (RES)
instruction. Executing this instruction takes the device out of the Deep Power-down mode.
The instruction can also be used to read, on Serial Data output (Q), the 8-bit Electronic
Signature, whose value for the M25P40 is 12h.
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 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 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 18.
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 Standby Power mode. If the
device was not previously in the Deep Power-down mode, the transition to the Standby
Power mode is immediate. If the device was previously in the Deep Power-down mode,
though, the transition to the Standby Power mode is delayed by t
, and Chip Select (S)
RES2
must remain High for at least t
(max), as specified in Table 19. Once in the Standby
RES2
Power mode, the device waits to be selected, so that it can receive, decode and execute
instructions.
Driving Chip Select (S) High after the 8-bit instruction byte has been received by the device,
but before the whole of the 8-bit Electronic Signature has been transmitted for the first time
(as shown in Figure 19), still ensures that the device is put into Standby Power mode. If the
device was not previously in the Deep Power-down mode, the transition to the Standby
Power mode is immediate. If the device was previously in the Deep Power-down mode,
though, the transition to the Standby Power mode is delayed by t
, and Chip Select (S)
RES1
must remain High for at least t
(max), as specified in Table 19. Once in the Standby
RES1
Power mode, the device waits to be selected, so that it can receive, decode and execute
instructions.
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