25LC640-ISLASHST datasheet(10/24 Pages) MICROCHIP

10 / 24 page

25AA640/25LC640

DS21223H-page 10

3.5

Read Status Register Instruction

(RDSR)

The Read Status Register instruction (RDSR) provides

access to the STATUS register. The STATUS register

may be read at any time, even during a write cycle. The

STATUS 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.

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 nonvolatile.

See Figure 3-6 for RDSR timing sequence.

FIGURE 3-6:

READ STATUS REGISTER TIMING SEQUENCE

654

WPEN

BP1

BP0

WEL

WIP

1011

1314

765

Instruction

Data from STATUS Register

High-Impedance

SCK

4567

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