S75WS256NDFBAWMB datasheet(58/216 Pages) SPANSION

58 / 216 page

S75WS256Nxx Based MCPs

S75WS-N-00_A0 February 17, 2005

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Inf o rmation

Notes

The DYBs can be set (programmed to 0) or cleared (erased to 1) as often as needed.

When the parts are first shipped, the PPBs are cleared (erased to 1) and upon power up or reset,

the DYBs can be set or cleared depending upon the ordering option chosen.

If the option to clear the DYBs after power up is chosen, (erased to 1), then the sectorsmay

be modified depending upon the PPB state of that sector (see Table 9.2).

The sectors would be in the protected state If the option to set the DYBs after power up is

chosen (programmed to 0).

It is possible to have sectors that are persistently locked with sectors that are left in the

dynamic state.

The DYB Set or Clear commands for the dynamic sectors signify protected or unprotected

state of the sectors respectively. However, if there is a need to change the status of the per-

sistently locked sectors, a few more steps are required. First, the PPB Lock Bit must be

cleared by either putting the device through a power-cycle, or hardware reset. The PPBs can

then be changed to reflect the desired settings. Setting the PPB Lock Bit once again locks

the PPBs, and the device operates normally again.

To achieve the best protection, it is recommended to execute the PPB Lock Bit Set command

early in the boot code and protect the boot code by holding WP# = VIL. Note that the PPB

and DYB bits have the same function when ACC = VHH as they do when ACC =VIH.

9.4

Persistent Protection Bit Lock Bit

The Persistent Protection Bit Lock Bit is a global volatile bit for all sectors. When set (programmed

to 0), it locks all PPBs and when cleared (programmed to 1), allows the PPBs to be changed. There

is only one PPB Lock Bit per device.

Notes

No software command sequence unlocks this bit unless the device is in the password pro-

tection mode; only a hardware reset or a power-up clears this bit.

The PPB Lock Bit must be set (programmed to 0) only after all PPBs are configured to the

desired settings.

9.5

Password Protection Method

The Password Protection Method allows an even higher level of security than the Persistent Sector

Protection Mode by requiring a 64 bit password for unlocking the device PPB Lock Bit. In addition

to this password requirement, after power up and reset, the PPB Lock Bit is set 0 to maintain the

password mode of operation. Successful execution of the Password Unlock command by entering

the entire password clears the PPB Lock Bit, allowing for sector PPBs modifications.

S75WS256NDFBAWMB Datasheet(PDF) 58 Page - SPANSION