S25FL040A Meet Spansion Inc., S25FL040A Datasheet - Page 28

• Manufacturer Part Number: S25FL040A
• Description: Small Sector For Boot And Parameter Storage 4-megabit Cmos 3.0 Volt Flash Memory With 50 Mhz Spi Bus Interface
• Manufacturer: Meet Spansion Inc.

28
9.13.1
SCK
CS#
SO
SI
Release from Deep Power Down and Read Electronic Signature (RES)
The device features an 8-bit Electronic Signature, which can be read using the RES command. See
Figure 9.14
be confused with the identification data obtained using the RDID command. The device offers the Electronic
Signature so that it can be used with previous devices that offered it; however, the Electronic Signature
should not be used for new designs, which should read the RDID data instead.
After the host system drives CS# low, it must write the RES command followed by 3 dummy bytes to SI (each
bit is latched on SI during the rising edge of SCK). The Electronic Signature is then output on SO; each bit is
shifted out on the falling edge of SCK. The RES operation is terminated by driving CS# high after the
Electronic Signature is read at least once. Additional clock cycles on SCK with CS# low cause the device to
output the Electronic Signature repeatedly.
When CS# is driven high, the device transitions from DP mode to the standby mode after a delay of t
previously described. The RES command always provides access to the Electronic Signature of the device
and can be applied even if DP mode has not been entered.
Any RES command issued while an erase, program, or WRSR operation is in progress not executed, and the
operation continues uninterrupted.
Hi-Z
0
and
1
Table 9.5
2
Command
3
4
for the command sequence and signature value. The Electronic Signature is not to
Read Electronic Signature (RES) Command Sequence
5
Figure 9.14 Release from Deep Power Down and
6
7
MSB
23 22 21
8
S25FL040A
9 10
3 Dummy Bytes
D a t a
28 29 30 31 32 33 34 35 36 37 38
3 2
Deep Power-down Mode
S h e e t
1
0
MSB
7
6
5
Electronic ID out
4
3
S25FL040A_00_B2 July 2, 2007
2
1
0
t
RES
Standby Mode
RES
, as