SST25VF080B datasheet(5/33 Pages) MICROCHIP

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DS20005045D-page 5

SST25VF080B

4.2

Write Protection

SST25VF080B provides software write protection. The

Write-Protect pin (WP#) enables or disables the lock-

down function of the STATUS Register. The Block Pro-

tection bits (BP3, BP2, BP1, BP0, and BPL) in the STA-

TUS register provide Write protection to the memory

array and the STATUS register. See Table 4-3 for the

Block Protection description.

4.2.1

WRITE PROTECTION PIN (WP#)

The Write-Protect (WP#) pin enables the lock-down

function of the BPL bit (bit 7) in the STATUS Register.

When WP# is driven low, the execution of the Write

STATUS Register (WRSR) instruction is determined by

the value of the BPL bit (see Table 4-1). When WP# is

high, the lock-down function of the BPL bit is disabled.

4.3

STATUS Register

The software STATUS Register provides status on

whether the flash memory array is available for any

read or write operation, whether the device is Write

enabled, and the state of the Memory Write-protected.

During an internal erase or program operation, the

STATUS Register may be read only to determine the

completion of an operation in progress. Table 4-2

describes the function of each bit in the software STA-

TUS Register.

4.3.1

BUSY

The BUSY bit determines whether there is an internal

Erase or Program operation in progress. A ‘1’ for the

BUSY bit indicates the device is busy with an operation

in progress. A ‘0’ indicates the device is ready for the

next valid operation.

4.3.2

WRITE ENABLE LATCH (WEL)

The Write Enable Latch bit indicates the status of the

internal memory Write Enable Latch. If the Write

Enable Latch bit is set to ‘1’, it indicates the device is

Write enabled. If the bit is set to ‘0’ (reset), it indicates

the device is not write enabled and does not accept any

memory write (program/erase) commands. The Write

Enable Latch bit is automatically reset under the follow-

ing conditions:

• Power-up

• Write Disable (WRDI) instruction completion

• Byte Program instruction completion

• Auto Address Increment (AAI) programming is

completed or reached its highest unprotected

memory address

• Sector Erase instruction completion

• Block Erase instruction completion

• Chip Erase instruction completion

• Write STATUS Register instructions

TABLE 4-1:

CONDITIONS TO EXECUTE WRITE STATUS REGISTER (

WRSR) INSTRUCTIONS

WP#

BPL

Execute WRSR Instructions

Not Allowed

Allowed

TABLE 4-2:

SOFTWARE STATUS REGISTER

Bit

Name

Function

Default at

Power-up

Read/Write

BUSY

1 = Internal Write operation is in progress

0 = No internal Write operation is in progress

WEL

1 = Device is memory Write enabled

0 = Device is not memory Write enabled

BP0

Indicate current level of block write protection (See Table 4-3)

R/W

BP1

Indicate current level of block write protection (See Table 4-3)

R/W

BP2

Indicate current level of block write protection (See Table 4-3)

R/W

BP3

Indicate current level of block write protection (See Table 4-3)

R/W

AAI

Auto Address Increment Programming status

1 = AAI programming mode

0 = Byte Program mode

BPL

1 = BP3, BP2, BP1, BP0 are read-only bits

0 = BP3, BP2, BP1, BP0 are read/writable

R/W

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