S29CD032G datasheet(30/93 Pages) SPANSION

30 / 93 page

S29CD032G

30606B0 March 22, 2004

Ad va n c e

In f o rm a t i o n

Table 11. Sector Protection Schemes

Table 11 contains all possible combinations of the DYB, PPB, and PPB lock relating

to the status of the sector.

In summary, if the PPB is set, and the PPB lock is set, the sector is protected and

the protection can not be removed until the next power cycle clears the PPB lock.

If the PPB is cleared, the sector can be dynamically locked or unlocked. The DYB

then controls whether or not the sector is protected or unprotected.

If the user attempts to program or erase a protected sector, the device ignores

the command and returns to read mode. A program command to a protected sec-

tor enables status polling for approximately 1 µs before the device returns to read

mode without having modified the contents of the protected sector. An erase

command to a protected sector enables status polling for approximately 50 µs

after which the device returns to read mode without having erased the protected

sector.

The programming of the DYB, PPB, and PPB lock for a given sector can be verified

by writing a DYB/PPB/PPB lock verify command to the device.

Persistent Sector Protection Mode Locking Bit

Like the password mode locking bit, a Persistent Sector Protection mode locking

bit exists to guarantee that the device remain in software sector protection. Once

set, the Persistent Sector Protection locking bit prevents programming of the

password protection mode locking bit. This guarantees that an unauthorized user

could not place the device in password protection mode.

Password Protection Mode

The Password Sector Protection Mode method allows an even higher level of se-

curity than the Persistent Sector Protection Mode. There are two main differences

between the Persistent Sector Protection and the Password Sector Protection

Mode:

When the device is first powered on, or comes out of a reset cycle, the PPB

Lock bit set to the locked state, rather than cleared to the unlocked state.

The only means to clear the PPB Lock bit is by writing a unique 64-bit Pass-

word to the device.

The Password Sector Protection method is otherwise identical to the Persistent

Sector Protection method.

DYB

PPB

PPB Lock

Sector State

Unprotected—PPB and DYB are changeable

Unprotected—PPB not changeable, DYB is changeable

Protected—PPB and DYB are changeable

Protected—PPB not changeable, DYB is changeable

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