2 write status register byte 1 – Rainbow Electronics AT25DF081A User Manual
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8715C–SFLSH–11/2012
AT25DF081A
11.2
Write Status Register Byte 1
The Write Status Register Byte 1 command is used to modify the SPRL bit of the Status Register and/or to perform
a Global Protect or Global Unprotect operation. Before the Write Status Register Byte 1 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 Byte 1 command, the CS pin must first be asserted and the opcode of 01h must
be clocked into the device followed by one byte of data. The one byte of data consists of the SPRL bit value, a
don’t care bit, four data bits to denote whether a Global Protect or Unprotect should be performed, and two addi-
tional don’t care bits (see
). 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 Regis-
ter will be reset back to a logical “0”. The values of bits five, four, three, and two and the state of the SPRL bit
before the Write Status Register Byte 1 command was executed (the prior state of the SPRL bit) will determine
whether or not a Global Protect or Global Unprotect will be performed. Please refer to
for more details.
The complete one byte of data must be clocked into the device before the CS pin is deasserted, and the CS pin
must be deasserted on even byte boundaries (multiples of eight bits); otherwise, the device will abort the operation,
the state of the SPRL bit will not change, no potential Global Protect or Unprotect will be performed, 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 Byte 1 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 logi-
cal “0”, the WP pin must be deasserted.
Figure 11-2. Write Status Register Byte 1
Table 11-3.
Write Status Register Byte 1 Format
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
SPRL
X
Global Protect/Unprotect
X
X
SCK
CS
SI
SO
MSB
2
3
1
0
0
0
0
0
0
0
0
6
7
5
4
OPCODE
10 11
9
8
14 15
13
12
1
MSB
D
X
D
D
D
D
X
X
STATUS REGISTER IN
BYTE 1
HIGH-IMPEDANCE