W78M32VP-XBX
3. The sectors would be in the protected state If the option to
set the DYBs after power up is chosen (programmed to “0”).
7. The Password Mode Lock Bit is not erasable.
8. The lower two address bits (A1–A0) are valid during the
Password Read, Password Program, and Password Unlock.
4. It is possible to have sectors that are persistently locked with
sectors that are left in the dynamic state.
9. The exact password must be entered in order for the unlocking
function to occur.
5. The DYB Set or Clear commands for the dynamic sectors
signify protected or unprotectedstate of the sectors respectively.
However, if there is a need to change the status of the persistently
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.
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
6. 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#/ACC = VIL. Note that the
PPB and DYB bits have the same function when WP#/ACC =
programming operation.
13. All further commands to the password region are disabled and
all operations are ignored.
V
HH as they do when ACC =VIH.
14. If the password is lost after setting the Password Mode Lock
Bit, there is no way to clear the PPB Lock Bit.
PERSISTENT PROTECTION BIT LOCK BIT
15. Entry command sequence must be issued prior to any of any
operation and it disables reads and writes for Sector 0. Reads
and writes for other sectors excluding Sector 0 are allowed.
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.
16. If the user attempts to program or erase a protected sector,
the device ignores the command and returns to read mode.
NOTES
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.
1. No software command sequence unlocks this bit unless the
device is in the password protection mode; only a hardware
reset or a power-up clears this bit.
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.
2. The PPB Lock Bit must be set (programmed to “0”) only after all
PPBs are conFigured to the desired settings.
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.
HARDWARE DATA PROTECTION METHODS
The device offers two main types of data protection at the sector
level via hardware control:
When WP#/ACC is at VIL, the either the highest or lowest
sector is locked (device specific).
There are additional methods by which intended or accidental
erasure of any sectors can be prevented via hardware means.
The following subsections describes these methods:
NOTES
1. 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 prevent
access.
WP#/ACC METHOD
The Write Protect feature provides a hardware method of protecting
one outermost sector. This function is provided by the WP#/ACC
pin and overrides the previously discussed Sector Protection/
Unprotection method.
2. The Password Program Command is only capable of
programming “0”s. Programming a “1” after a cell is
programmed as a “0” results in a time-out with the cell as a “0”.
If the system asserts VIL on the WP#/ACC pin, the device disables
program and erase functions in the highest or lowest sector
independently of whether the sector was protected or unprotected
using the method described in Advanced Sector Protection/
Unprotection.
3. The password is all “1”s when shipped from the factory.
4. All 64-bit password combinations are valid as a password.
5. There is no means to verify what the password is after it is set.
6. The Password Mode Lock Bit, once set, prevents reading
the 64-bit password on the data bus and further password
programming.
If the system asserts VIH on the WP#/ACC pin, the device
reverts to whether the boot sectors were last set to be protected
Microsemi Corporation reserves the right to change products or specifications without notice.
August 2011 © 2011 Microsemi Corporation. All rights reserved.
Rev. 15
10
Microsemi Corporation • (602) 437-1520 • www.microsemi.com
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