Instructions
M25P20
6.4
Read Status Register (RDSR)
The Read Status Register (RDSR) instruction allows the Status Register to be read. The
Status Register may be read at any time, even while a Program, Erase or Write Status
Register cycle is in progress. When one of these cycles is in progress, it is recommended to
check the Write In Progress (WIP) bit before sending a new instruction to the device. It is
also possible to read the Status Register continuously, as shown in Figure 10.
Table 6.
Status Register Format
b7
b0
SRWD
0
0
0
BP1
BP0
WEL
WIP
Status Register Write Protect
Block Protect Bits
Write Enable Latch Bit
Write In Progress Bit
The status and control bits of the Status Register are as follows:
6.4.1
6.4.2
6.4.3
WIP bit
The Write In Progress (WIP) bit indicates whether the memory is busy with a Write Status
Register, Program or Erase cycle. When set to 1, such a cycle is in progress, when reset to
0 no such cycle is in progress.
WEL bit
The Write Enable Latch (WEL) bit indicates the status of the internal Write Enable Latch.
When set to 1 the internal Write Enable Latch is set, when set to 0 the internal Write Enable
Latch is reset and no Write Status Register, Program or Erase instruction is accepted.
BP1, BP0 bits
The Block Protect (BP1, BP0) bits are non-volatile. They define the size of the area to be
software protected against Program and Erase instructions. These bits are written with the
Write Status Register (WRSR) instruction. When one or both of the Block Protect (BP1,
BP0) bits is set to 1, the relevant memory area (as defined in Table 2) becomes protected
against Page Program (PP) and Sector Erase (SE) instructions. The Block Protect (BP1,
BP0) bits can be written provided that the Hardware Protected mode has not been set. The
Bulk Erase (BE) instruction is executed if, and only if, both Block Protect (BP1, BP0) bits are
0.
6.4.4
SRWD bit
The Status Register Write Disable (SRWD) bit is operated in conjunction with the Write
Protect (W) signal. The Status Register Write Disable (SRWD) bit and Write Protect (W)
signal allow the device to be put in the Hardware Protected mode (when the Status Register
Write Disable (SRWD) bit is set to 1, and Write Protect (W) is driven Low). In this mode, the
non-volatile bits of the Status Register (SRWD, BP1, BP0) become read-only bits and the
Write Status Register (WRSR) instruction is no longer accepted for execution.
20/50
NUMONYX [ NUMONYX B.V ]
