M25PE20, M25PE10
Instructions
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 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 11.
The status 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, 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, 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 3) becomes protected
against Page Program (PP), Page Erase (PE), Sector Erase (SE) and SubSector Erase
(SSE) 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:
●
all Block Protect (BP1, BP0) bits are 0
●
the Lock Register protection bits are not all set to ‘1’.
6.4.4
SRWD bit
The Status Register Write Disable (SRWD) bit is operated in conjunction with the Write
Protect (W) signal. When the Status Register Write Disable (SRWD) bit is set to ‘1’, and
Write Protect (W) is driven Low, the non-volatile bits of the Status Register (SRWD, BP1,
BP0) become read-only bits. In such a state, as the Write Status Register (WRSR)
instruction is no longer accepted for execution, the definition of the size of the Write
Protected area cannot be further modified.
(1) (2)
Table 9.
Status Register format
b7
b0
SRWD
0
0
0
BP1
BP0
WEL(3)
WIP(3)
1. SRWD = Status Register Write Protect bit; BP0, BP1 = block protect bits (only available with T9HX).
2. The BP bits and the SRWD bit exist only in the T9HX process.
3. WEL (Write Enable Latch) and WIP (Write In Progress) are volatile read-only bits (WEL is set and reset by
specific instructions; WIP is automatically set and reset by the internal logic of the device).
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NUMONYX [ NUMONYX B.V ]
