58 S29WS128J/064J S29WS-J_00_A6 May 11, 2006
Data Sheet
Secured Silicon Sector Protection Bit Program Command
To protect the Secured Silicon Sector, write the Secured Silicon Sector Protect command sequence
while in the Secured Silicon Sector mode. After issuing “OW/48h” at the fourth bus cycle, the de
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vice requires a time out period of approximately 150
µs
to protect the Secured Silicon Sector.
Then, by writing “OPBP/48” at the fifth bus cycle, the device outputs verify data at DQ0. If DQ0
= 1, then the Secured Silicon Sector is protected. If not, then the system must repeat this pro
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gram sequence from the fourth cycle of “OPBP/48h”. Exiting the Secured Silicon Sector Protection
Mode Locking Bit Program command is accomplished by writing the Secured Silicon Sector Exit
command or Read/Reset command.
PPB Lock Bit Set Command
The PPB Lock Bit Set command is used to set the PPB Lock bit if it is cleared either at reset or if
the Password Unlock command was successfully executed. There is no PPB Lock Bit Clear com
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mand. Once the PPB Lock Bit is set, it cannot be cleared unless the device is taken through a
power-on clear or the Password Unlock command is executed. Upon setting the PPB Lock Bit, the
PPBs are latched. If the Password Mode Locking Bit is set, the PPB Lock Bit status is reflected as
set, even after a power-on reset cycle. Exiting the PPB Lock Bit Set command is accomplished by
writing the Secured Silicon Exit command, only while in the Persistent Sector Protection Mode.
DPB Write/Erase/Status Command
The DPB Write command is used to set or clear a DPB for a given sector. The high order address
bits (Amax–A11) are issued at the same time as the code 01h or 00h on DQ7-DQ0. All other DQ
data bus pins are ignored during the data write cycle. The DPBs are modifiable at any time, re
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gardless of the state of the PPB or PPB Lock Bit. If the PPB is set, the sector is protected regardless
of the value of the DPB. If the PPB is cleared, setting the DPB to a 1 protects the sector from
programs or erases. Since this is a volatile bit, removing power or resetting the device will clear
the DPBs. The programming of the DPB for a given sector can be verified by writing a DPB Status
command to the device. Exiting the DPB Write/Erase command is accomplished by writing the
Read/Reset command. Exiting the DPB Status command is accomplished by writting the Secured
Silicon Sector Exit command
Password Unlock Command
The Password Unlock command is used to clear the PPB Lock Bit so that the PPBs can be unlocked
for modification, thereby allowing the PPBs to become accessible for modification. The exact pass
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word must be entered in order for the unlocking function to occur. This command cannot be issued
any faster than 2 µs at a time to prevent a hacker from running through the all 64-bit combina
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tions in an attempt to correctly match a password. If the command is issued before the 2 µs
execution window for each portion of the unlock, the command will be ignored.
The Password Unlock function is accomplished by writing Password Unlock command and data to
the device to perform the clearing of the PPB Lock Bit. The password is 64 bits long, so the user
must write the Password Unlock command 4 times. A1 and A0 are used for matching. Writing the
Password Unlock command is not address order specific. The lower address A1–A0= 00, the next
Password Unlock command is to A1–A0= 01, then to A1–A0= 10, and finally to A1–A0= 11.
Once the Password Unlock command is entered for all four words, the RDY pin goes LOW indicat-
ing that the device is busy. Also, reading the Bank D results in the DQ6 pin toggling, indicating
that the Password Unlock function is in progress. Reading the other bank returns actual array
data. Approximately 1µs is required for each portion of the unlock. Once the first portion of the
password unlock completes (RDY is not driven and DQ6 does not toggle when read), the Password
Unlock command is issued again, only this time with the next part of the password. Four Password
Unlock commands are required to successfully clear the PPB Lock Bit. As with the first Password
Unlock command, the RDY signal goes LOW and reading the device results in the DQ6 pin toggling
on successive read operations until complete. It is the responsibility of the microprocessor to keep
