25C640 Microchip Technology, Inc., 25C640 Datasheet - Page 11

• Manufacturer Part Number: 25C640
• Description: The 25AA640 is a 64K-bit Serial Electrically Erasable Prom With Memory Accessed Via a Simple Serial Peripheral Interface (SPI™) Compatible Serial Bus
• Manufacturer: Microchip Technology, Inc.

3.5
The Read Status Register (RDSR) instruction provides
access to the status register. The status register may
be read at any time, even during a write cycle. The sta-
tus register is formatted as follows:
The Write-In-Process (WIP) bit indicates whether the
25XX640 is busy with a write operation. When set to a
‘1’, a write is in progress, when set to a ‘0’, no write is
in progress. This bit is read only.
FIGURE 3-6:
WPEN
2001 Microchip Technology Inc.
SCK
SO
CS
7
SI
Read Status Register (RDSR)
X
6
0
X
5
0
X
4
0
1
READ STATUS REGISTER TIMING SEQUENCE
High Impedance
BP1
3
0
2
Instruction
BP0
0
2
3
0
WEL
4
1
1
5
WIP
0
0
6
1
7
The Write Enable Latch (WEL) bit indicates the status
of the write enable latch. When set to a ‘1’, the latch
allows writes to the array and status register, when set
to a ‘0’, the latch prohibits writes to the array and status
register. The state of this bit can always be updated via
the WREN or WRDI commands regardless of the state
of write protection on the status register. This bit is read
only.
The Block Protection (BP0 and BP1) bits indicate
which blocks are currently write protected. These bits
are set by the user issuing the WRSR instruction.
These bits are non-volatile.
See Figure 3-6 for RDSR timing sequence.
7
8
6
25AA640/25LC640
9
Data from Status Register
10
5
11
4
12
3
13
2
14
1
DS21223E-page 11
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