SST25VF080B datasheet(5/32 Pages) MICROCHIP

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DS20005045C-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-Protec-

tion bits (BP3, BP2, BP1, BP0, and BPL) in the status

and the status register. See Table 4-3 for the Block-Pro-

tection description.

4.2.1

WRITE PROTECT 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 protection.

During an internal Erase or Program operation, the sta-

tus register may be read only to determine the comple-

tion of an operation in progress. Table 4-2 describes

the function of each bit in the software status 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

following 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) INSTRUCTION

WP#

BPL

Execute WRSR Instruction

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)

1R/W

BP1

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

1R/W

BP2

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

1R/W

BP3

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

0R/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

0R/W

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