S75WS256NDFBAWMB datasheet(59/216 Pages) SPANSION

59 / 216 page

February 17, 2005 S75WS-N-00_A0

S75WS256Nxx Based MCPs

Advance

Information

Notes

There is no special addressing order required for programming the password. Once the

Password is written and verified, the Password Mode Locking Bit must be set in order to pre-

vent access.

The Password Program Command is only capable of programming 0s. Programming a 1 after

a cell is programmed as a 0 results in a time-out with the cell as a 0.

The password is all 1s when shipped from the factory.

All 64-bit password combinations are valid as a password.

There is no means to verify what the password is after it is set.

The Password Mode Lock Bit, once set, prevents reading the 64-bit password on the data

bus and further password programming.

The Password Mode Lock Bit is not erasable.

The lower two address bits (A1–A0) are valid during the Password Read, Password Program,

and Password Unlock.

The exact password must be entered in order for the unlocking function to occur.

10. The Password Unlock command cannot be issued any faster than 1 µs at a time to prevent

a hacker from running through all the 64-bit combinations in an attempt to correctly match

a password.

11. Approximately 1 µs is required for unlocking the device after the valid 64-bit password is

given to the device.

12. Password verification is only allowed during the password programming operation.

13. All further commands to the password region are disabled and all operations are ignored.

14. If the password is lost after setting the Password Mode Lock Bit, there is no way to clear the

PPB Lock Bit.

15. Entry command sequence must be issued prior to any of any operation and it disables reads

and writes for Bank 0. Reads and writes for other banks excluding Bank 0 are allowed.

16. If the user attempts to program or erase a protected sector, the device ignores the com-

mand and returns to read mode.

17. A program or erase command to a protected sector enables status polling and returns to

read mode without having modified the contents of the protected sector.

18. The programming of the DYB, PPB, and PPB Lock for a given sector can be verified by writing

individual status read commands DYB Status, PPB Status, and PPB Lock Status to the

device.

S75WS256NDFBAWMB Datasheet(PDF) 59 Page - SPANSION