FM25V20 – 2Mb SPI F-RAM
Sleep Mode
Enter Sleep
Mode
A
low power mode called Sleep Mode is
implemented on the FM25V20 device. The device
will enter this low power state when the SLEEP op-
code B9h is clocked-in and a rising edge of /S is
applied. Once in sleep mode, the C and D pins are
ignored and Q will be high-Z, but the device
continues to monitor the /S pin. On the next falling
edge of /S, the device will return to normal operation
within tREC (400 s max.). The Q pin remains in a hi-
Z state during the wakeup period. The device will not
necessarily respond to an opcode within the wakeup
period. To start the wakeup procedure, the controller
may send a “dummy” read, for example, and wait the
remaining tREC time.
S
C
D
Q
Figure 12. Sleep Mode Entry
Device ID
The FM25V20 device can be interrogated for its manufacturer, product identification, and die revision. The RDID
op-code 9Fh allows the user to read the manufacturer ID and product ID, both of which are read-only bytes. The
JEDEC-assigned manufacturer ID places the Ramtron identifier in bank 7, therefore there are six bytes of the
continuation code 7Fh followed by the single byte C2h. There are two bytes of product ID, which includes a Family
code, a Density code, a Sub code, and Product Revision code.
Table 5. Manufacturer and Product ID
Bit
7
0
0
0
0
0
0
1
6
1
1
1
1
1
1
1
5
1
1
1
1
1
1
0
4
1
1
1
1
1
1
0
3
1
1
1
1
1
1
0
2
1
1
1
1
1
1
0
1
1
1
1
1
1
1
1
0
1
1
1
1
1
1
0
Hex
7F
7F
7F
7F
7F
7F
C2
Manufacturer ID
Continuation code
Continuation code
Continuation code
Continuation code
Continuation code
Continuation code
JEDEC assigned Ramtron C2h in bank 7
Family
0
Sub
Density
Hex
25h
Device ID (1st Byte)
Device ID (2nd Byte)
0
1
0
0
Rev.
0
0
1
0
1
0
Density: 03h=512K, 04h=1M, 05h=2M, 06h=4M
00h=FM25V20
Rsvd
0
0
0
0
0
00h
S
C
. . . . . . .
D
Q
9Fh
C2h
25h
7Fh
…
7Fh
6
00h
1
Six bytes of continuation code 7Fh
Figure 13. Read Device ID
Rev. 3.0
August 2012
Page 9 of 17
RAMTRON [ RAMTRON INTERNATIONAL CORPORATION ]
