AM29N323D Datasheet, PDF (17/48 Pages) Advanced Micro Devices – 32 Megabit (2 M x 16-Bit) CMOS 1.8 Volt-only Simultaneous Read/Write, Burst Mode Flash Memory

the system was writing to the read mode. Once erasure
begins, however, the device ignores reset commands
until the operation is complete.
The reset command may be written between the
sequence cycles in a program command sequence
before programming begins. This resets the bank to
which the system was writing to the read mode. If the
program command sequence is written to a bank that
is in the Erase Suspend mode, writing the reset
command returns that bank to the erase-suspend-read
mode. Once programming begins, however, the device
ignores reset commands until the operation is com-
plete.
The reset command may be written between the
sequence cycles in an autoselect command sequence.
Once in the autoselect mode, the reset command must
be written to return to the read mode. If a bank entered
the autoselect mode while in the Erase Suspend mode,
writing the reset command returns that bank to the
erase-suspend-read mode.
If DQ5 goes high during a program or erase operation,
writing the reset command returns the banks to the
read mode (or erase-suspend-read mode if that bank
was in Erase Suspend).
Autoselect Command Sequence
The autoselect command sequence allows the host
system to read several identifier codes at specific
addresses:
Identifier Code
Manufacturer ID
Device ID
Sector Protect Verify
Revision ID
Address
(BA)00h
(BA)01h
(SA)02h
(BA)03h
Table 4 shows the address and data requirements. The
autoselect command sequence may be written to an
address within a bank that is either in the read or
erase-suspend-read mode. The autoselect command
may not be written while the device is actively program-
ming or erasing in the other bank.
The autoselect command sequence is initiated by first
writing two unlock cycles. This is followed by a third
write cycle that contains the bank address and the
autoselect command. The bank then enters the
autoselect mode. The system may read at any address
within the same bank any number of times without ini-
tiating another autoselect command sequence.
The system must write the reset command to return to
the read mode (or erase-suspend-read mode if the
bank was previously in Erase Suspend).
Program Command Sequence
Programming is a four-bus-cycle operation. The
program command sequence is initiated by writing two
unlock write cycles, followed by the program set-up
command. The program address and data are written
next, which in turn initiate the Embedded Program
algorithm. The system is not required to provide further
controls or timings. The device automatically provides
internally generated program pulses and verifies the
programmed cell margin. Table 4 shows the address
and data requirements for the program command
sequence.
When the Embedded Program algorithm is complete,
that bank then returns to the read mode and addresses
are no longer latched. The system can determine the
status of the program operation by monitoring DQ7 or
DQ6/DQ2. Refer to the Write Operation Status section
for information on these status bits.
Any commands written to the device during the
Embedded Program Algorithm are ignored. Note that a
hardware reset immediately terminates the program
operation. The program command sequence should be
reinitiated once that bank has returned to the read
mode, to ensure data integrity.
Programming is allowed in any sequence and across
sector boundaries. A bit cannot be programmed
from “0” back to a “1.” Attempting to do so may
cause that bank to set DQ5 = 1, or cause the DQ7 and
DQ6 status bit to indicate the operation was suc-
cessful. However, a succeeding read will show that the
data is still “0.” Only erase operations can convert a “0”
to a “1.”
Unlock Bypass Command Sequence
The unlock bypass feature allows the system to
program to a bank faster than using the standard
program command sequence. The unlock bypass
command sequence is initiated by first writing two
unlock cycles. This is followed by a third write cycle
containing the unlock bypass command, 20h. That
bank then enters the unlock bypass mode. A two-cycle
unlock bypass program command sequence is all that
is required to program in this mode. The first cycle in
this sequence contains the unlock bypass program
command, A0h; the second cycle contains the program
address and data. Additional data is programmed in
the same manner. This mode dispenses with the initial
two unlock cycles required in the standard program
command sequence, resulting in faster total program-
ming time. The host system may also initiate the chip
erase and sector erase sequences in the unlock
bypass mode. The erase command sequences are
four cycles in length instead of six cycles. Table 4
shows the requirements for the command sequence.
During the unlock bypass mode, only the Unlock
Bypass Program and Unlock Bypass Reset commands
are valid. To exit the unlock bypass mode, the system
must issue the two-cycle unlock bypass reset
command sequence. The first cycle must contain the
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Am29N323D
August 8, 2002