AT26F004-SSU ATMEL [ATMEL Corporation], AT26F004-SSU Datasheet - Page 22

• Manufacturer Part Number: AT26F004-SSU
• Description: 4-megabit 2.7-volt Only Serial Firmware DataFlash Memory
• Manufacturer: ATMEL [ATMEL Corporation]

10.2
Write Status Register
The Write Status Register command is used to modify the SPRL bit of the Status Register.
Before the Write Status Register command can be issued, the Write Enable command must
have been previously issued to set the WEL bit in the Status Register to a logical “1”.
To issue the Write Status Register command, the CS pin must first be asserted and the opcode
of 01h must be clocked into the device. After the opcode has been clocked in, one byte of data
comprised of the SPRL bit value and seven don't care bits must be clocked in. Any additional
data bytes that are sent to the device will be ignored. When the CS pin is deasserted, the SPRL
bit in the Status Register will be modified, and the WEL bit in the Status Register will be reset
back to a logical “0”. The complete one byte of data must be clocked into the device before the
CS# pin is deasserted; otherwise, the device will abort the operation, the state of the SPRL bit
will not change, and the WEL bit in the Status Register will be reset back to the logical “0” state.
If the WP pin is asserted, then the SPRL bit can only be set to a logical “1”. If an attempt is made
to reset the SPRL bit to a logical “0” while the WP pin is asserted, then the Write Status Register
command will be ignored, and the WEL bit in the Status Register will be reset back to the logical
“0” state. In order to reset the SPRL bit to a logical “0”, the WP pin must be deasserted.
Figure 10-2. Write Status Register
CS
0
1
2
3
4
5
6
7
8
9
10 11
12
13
14 15
SCK
OPCODE
STATUS REGISTER IN
SI
0
0
0
0
0
0
0
1
D
X
X
X
X
X
X
X
MSB
MSB
HIGH-IMPEDANCE
SO
AT26F004
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3588A–DFLSH–10/05