IS25LP256D-RGLA3 datasheet(35/174 Pages) ISSI

35 / 174 page

IS25LP256D

IS25WP256D

Integrated Silicon Solution, Inc.- www.issi.com

Rev A6

04/15/2019

Persistent Protection Bits (PPBs)

The Persistent Protection Bits (PPBs) are unique for each sector/block and non-volatile (refer to Figure 7.1, Table

7.2, and Table 7.3). It is programmed individually but must be erased as a group, similar to the way individual words

may be programmed in the main array but an entire sector/block must be erased at the same time. The PPBs have

the same endurances as the Flash memory. Preprogramming and verification prior to erasure are handled by the

device, and therefore do not require system monitoring. Programming a PPB bit requires the typical page

programming time. Erasing all the PPBs requires typical sector erase time. During PPB bit programming and PPB

bit erasing, status is available by reading the Status Register or Extended Read Register. Reading of a PPB bit

requires the initial access time of the device.

Notes:

1. Each PPB is individually programmed

to “0” and all are erased to “1” in parallel.

2. The PPB Lock bit must be cleared first before changing the status of a PPB.

3. While programming PPB, array data cannot be read from any sectors/blocks.

4. When reading the PPB of the desired sector/block the address should be location zero within the sector/block. The high

order address bits not used must be zero.

5. There are no means for individually erasing a specific PPB and no specific sector/block address is required for this operation.

6. The state of the PPB for a given sector/block can be verified by using a PPB Read command.

7. When the parts are first shipped, the PPBs are cleared (erased to “1”).

Dynamic Protection Bits (DYBs)

Dynamic Protection Bits (DYBs) are volatile and unique for each sector/block and can be individually modified.

DYBs only control the protection for unprotected sectors/blocks that have their PPBs cleared (erased to

“1”). By

issuing the Write DYB command, the DYBs are cleared

to “0” or set to “1”, thus placing each sector/block in the

protected or unprotected state respectively. This feature allows software to easily protect sectors/blocks against

inadvertent changes, yet does not prevent the easy removal of protection when changes are needed. The DYBs

can be set or cleared as often as needed as they are volatile bits.

Persistent Protection Bit (PPB) Lock Bit

The PPB Lock bit is a volatile bit for protecting all PPB bits. When

cleared to “0”, it locks all PPBs and when set to

“1”, it allows the PPBs to be changed. . If the PPB Lock bit is “0”, the PPB Program or Erase command does not

execute and fails without programming or erasing the PPB.

In Persistent Protection mode, the PPB Lock bit

is set to “1” during power up or Hardware Reset. When cleared to

“0”, no software command sequence can set the PPB Lock bit to “1”, only another Hardware Reset or power-up

can set the PPB Lock bit.

In the Password Protection mode, the PPB Lock bit is cleared to “0” during power up or a Hardware Reset during

power up or a Hardware Reset during power up or a Hardware Reset. The PPB

Lock bit can only be set to “1” by

the Password Unlock command.

The PPB Lock bit must be cleared

to “0” only after all PPBs are configured to the desired settings.

IS25LP256D-RGLA3 Datasheet(PDF) 35 Page - Integrated Silicon Solution, Inc

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