S79FL256S datasheet(50/111 Pages) CYPRESS

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Document Number: 002-00518 Rev. *D

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S79FL256S/S79FL512S

8.4.3

Dynamic Protection Bits

Dynamic Protection Bits are volatile and unique for each sector and can be individually modified. DYB only control the protection for

sectors that have their PPB set to 1. By issuing the DYB Write command, a DYB is cleared to 0 or set to 1, thus placing each sector

in the protected or unprotected state respectively. This feature allows software to easily protect sectors 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.

8.4.4

PPB Lock Bit (PPBL[0])

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.

The PLBWR command is used to clear the PPB Lock bit to 0. The PPB Lock Bit must be cleared to 0 only after all the PPBs are

configured to the desired settings.

In Persistent Protection mode, the PPB Lock is set to 1 during POR or a 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 POR or a hardware reset. The PPB Lock bit can only be

set to 1 by the Password Unlock command.

8.4.5

Sector Protection States Summary

Each sector can be in one of the following protection states:



Unlocked — The sector is unprotected and protection can be changed by a simple command. The protection state defaults to

unprotected after a power cycle, software reset, or hardware reset.



Dynamically Locked — A sector is protected and protection can be changed by a simple command. The protection state is not

saved across a power cycle or reset.



Persistently Locked — A sector is protected and protection can only be changed if the PPB Lock Bit is set to 1. The protection

state is non-volatile and saved across a power cycle or reset. Changing the protection state requires programming and or erase of

the PPB bits

Table 36. Sector Protection States

Protection Bit Values

Sector State

PPB Lock

PPB

DYB

Unprotected – PPB and DYB are changeable

Protected – PPB and DYB are changeable

Unprotected – PPB not changeable, DYB is changeable

Protected – PPB not changeable, DYB is changeable

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