AM29PDL640G Datasheet, PDF (34/61 Pages) SPANSION – 64 Megabit (4 M x 16-Bit) CMOS 3.0 Volt-only, Simultaneous Read/Write Flash Memory with Enhanced VersatileIO Control

PRELIMINARY
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 ac-
cessible for modification. The exact password 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 all
64-bit combinations 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.
Once the Password Unlock command is entered, the
RY/BY# indicates that the device is busy. Approxi-
mately 2 µs is required for each portion of the unlock.
Once the first portion of the password unlock com-
pletes (RY/BY# is not low or DQ6 does not toggle
when read), the Password Unlock command and next
part of the password are written. The system must
thus monitor RY/BY# or the status bits to confirm
when to write the next portion of the password.
Note that immediately following successful unlock,
write the SecSi Sector exit command before attempt-
ing to verify, program, or erase the PPBs.
PPB Program Command
The PPB Program command is used to program, or
set, a given PPB. Each PPB is individually pro-
grammed (but is bulk erased with the other PPBs).
The specific sector address (A21–A12) are written at
the same time as the program command 60h with A6
= 0. If the PPB Lock Bit is set and the corresponding
PPB is set for the sector, the PPB Program command
will not execute and the command will time-out without
programming the PPB.
After programming a PPB, two additional cycles are
needed to determine whether the PPB has been pro-
grammed with margin. If the PPB has been pro-
grammed without margin, the program command
should be reissued to improve the program margin.
Also note that the total number of PPB program/erase
cycles is limited to 100 cycles. Cycling the PPBs be-
yond 100 cycles is not guaranteed.
The PPB Program command does not follow the Em-
bedded Program algorithm.
All PPB Erase Command
The All PPB Erase command is used to erase all
PPBs in bulk. There is no means for individually eras-
ing a specific PPB. Unlike the PPB program, no spe-
cific sector address is required. However, when the
PPB erase command is written all Sector PPBs are
erased in parallel. If the PPB Lock Bit is set the ALL
PPB Erase command will not execute and the com-
mand will time-out without erasing the PPBs. After
erasing the PPBs, two additional cycles are needed to
determine whether the PPB has been erased with
margin. If the PPBs has been erased without margin,
the erase command should be reissued to improve the
program margin.
It is the responsibility of the user to preprogram all
PPBs prior to issuing the All PPB Erase command. If
the user attempts to erase a cleared PPB, over-era-
sure may occur making it difficult to program the PPB
at a later time. Also note that the total number of PPB
program/erase cycles is limited to 100 cycles. Cycling
the PPBs beyond 100 cycles is not guaranteed.
DYB Write Command
The DYB Write command is used for setting the DYB,
which is a volatile bit that is cleared at reset. There is
one DYB per sector. If the PPB is set, the sector is
protected regardless of the value of the DYB. If the
PPB is cleared, setting the DYB 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 DYBs. The bank address is latched when the com-
mand is written.
PPB Lock Bit Set Command
The PPB Lock Bit set command is used for setting the
DYB, which is a volatile bit that is cleared at reset.
There is one DYB per sector. If the PPB is set, the
sector is protected regardless of the value of the DYB.
If the PPB is cleared, setting the DYB to a 1 protects
the sector from programs or erases. Since this is a vol-
atile bit, removing power or resetting the device will
clear the DYBs. The bank address is latched when the
command is written.
PPB Status Command
The programming of the PPB for a given sector can be
verified by writing a PPB status verify command to the
device.
PPB Lock Bit Status Command
The programming of the PPB Lock Bit for a given sec-
tor can be verified by writing a PPB Lock Bit status
verify command to the device.
Note that immediately following the PPB Lock Status
Command write the SecSi Sector Exit command be-
fore attempting to verify, program, or erase the PPBs.
Sector Protection Status Command
The programming of either the PPB or DYB for a given
sector or sector group can be verified by writing a Sec-
tor Protection Status command to the device.
Note that there is no single command to independently
verify the programming of a DYB for a given sector
group.
February 26, 2003
Am29PDL640G
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