
MR25H10
SPI COMMUNICATIONS PROTOCOL
Write Enable (WREN)
The Write Enable (WREN) command sets the Write Enable Latch (WEL) bit in the status register to 1. The
WEL bit must be set prior to writing in the status register or the memory. The WREN command is entered
by driving CS low, sending the command code, and then driving CS high.
Figure 2.2 WREN
CS
Mode 3
0
1
2
3
4
5
6
7
Mode 3
SCK
Mode 0
Instruction (06h)
Mode 0
SI
0
0
0
0
0
1
1
0
SO
High Impedance
Write Disable (WRDI)
The Write Disable (WRDI) command resets the WEL bit in the status register to 0. This prevents writes to
status register or memory. The WRDI command is entered by driving CS low, sending the command code,
and then driving CS high.
The WEL bit is reset to 0 on power-up or completion of WRDI.
Figure 2.3 WRDI
CS
Mode 3
0
1
2
3
4
5
6
7
Mode 3
SCK
Mode 0
Instruction (04h)
Mode 0
SI
0
0
0
0
0
1
0
0
SO
High Impedance
Write Status Register (WRSR)
The Write Status Register (WRSR) command allows new values to be written to the Status Register. The
WRSR command is not executed unless the Write Enable Latch (WEL) has been set to 1 by executing a
WREN command while pin WP and bit SRWD correspond to values that make the status register writable
as seen in table 2.4. Status Register bits are non-volatile with the exception of the WEL which is reset to 0
upon power cycling.
Copyright ? Everspin Technologies 2013
6
MR25H10 Rev. 9, 4/2013