W78M32VP-XBX
The reset command may be written during an Autoselect
2. Dynamically locked. The selected sectors are protected and
can be altered via software commands.
command sequence.
If a sector has entered the Autoselect mode while in the
Erase Suspend mode, writing the reset command returns
that sector to the erase-suspend-read mode.
3. Unlocked. The sectors are unprotected and can be erased
and/or programmed.
PERSISTENT PROTECTION BITS
If DQ1 goes high during a Write Buffer Programming
operation, the system must write the “Write to Buffer abort
Reset” command sequence to RESET the device to reading
array data. The standard RESET command does not work
during this condition.
The Persistent Protection Bits are unique and nonvolatile for each
sector and have the same endurances as the Flash memory.
Preprogramming and verification prior to erasure are handled by
the device, and therefore do not require system monitoring.
To exit the unlock bypass mode, the system must issue a
two-cycle unlock bypass reset command sequence [see
Command Definitions for details].
NOTES
1. Each PPB is individually programmed and all are erased in
parallel.
2. While programming PPB for a sector, array data can be read
from any other sector, except Sector 0 (used for Data# Polling)
and the sector in which sector PPB is being programmed.
ADVANCED SECTOR PROTECTION/
UNPROTECTION
The Advanced Sector Protection/Unprotection feature disables or
enables programming or erase operations in any or all sectors and
can be implemented through software and/or hardware methods,
which are independent of each other. This section describes the
various methods of protecting data stored in the memory array. An
overview of these methods in shown in Figure 8.
3. Entry command disables reads and writes for the sector
selected.
4. Reads within that sector return the PPB status for that sector.
5. All Reads must be performed using the read mode.
6. The specific sector address (A22-A16) are written at the same
time as the program command.
LOCK REGISTER
7. If the PPB Lock Bit is set, the PPB Program or erase command
does not execute and times-out without programming or
erasing the PPB.
As shipped from the factory, all devices default to the persistent
mode when power is applied, and all sectors are unprotected. The
device programmer or host system must then choose which sector
protection method to use. Programming (setting to “0”) any one of
the following two one-time programmable, non-volatile bits locks
the part permanently in that mode:
8. There are no means for individually erasing a specific PPB
and no specific sector address is required for this operation.
9. Exit command must be issued after the execution which resets
the device to read mode and reenables reads and writes for
Sector 0.
Lock Register Persistent Protection Mode Lock Bit (DQ1)
Lock Register Password Protection Mode Lock Bit (DQ2)
10. The programming state of the PPB for a given sector can be
verified by writing a PPB Status Read Command to the device
as described by the flow chart shown in Figure 9.
NOTES
1. If the password mode is chosen, the password must be
programmed before setting the corresponding lock register bit.
DYNAMIC PROTECTION BITS
2. After the Lock Register Bits Command Set Entry command
sequence is written, reads and writes for Sector 0 are disabled,
while reads from other sectors are allowed until exiting this
mode.
Dynamic Protection Bits are volatile and unique for each sector
and can be individually modified. DYBs only control the protection
scheme for unprotected sectors that have their PPBs cleared
(erased to “1”). By issuing the DYB Set or Clear command
sequences, the DYBs are set (programmed to “0”) or cleared
(erased to “1”), thus placing each sector in the protected or
unprotected state respectively. This feature allows software to
easily protect sectors against inadvertent changes yet does not
prevent the easy removal of protection when changes are needed.
3. If both lock bits are selected to be programmed (to zeros) at
the same time, the operation aborts.
4. Once the Password Mode Lock Bit is programmed, the
Persistent Mode Lock Bit is permanently disabled, and no
changes to the protection scheme are allowed. Similarly, if the
Persistent Mode Lock Bit is programmed, the Password Mode
is permanently disabled.
NOTES
1. 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.
After selecting a sector protection method, each sector can operate
in any of the following three states:
1. Constantly locked. The selected sectors are protected and
can not be reprogrammed unless PPB lock bit is cleared via a
password, hardware reset, or power cycle.
2. If the option to clear the DYBs after power up is chosen, (erased
to “1”), then the sectors may be modified depending upon the
PPB state of that sector (see Table 20).
Microsemi Corporation reserves the right to change products or specifications without notice.
August 2011 © 2011 Microsemi Corporation. All rights reserved.
Rev. 15
9
Microsemi Corporation • (602) 437-1520 • www.microsemi.com
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