AM29F004B Datasheet, PDF (17/37 Pages) Advanced Micro Devices – 4 Megabit (512 K x 8-Bit) CMOS 5.0 Volt-only Boot Sector Flash Memory

ADVANCE INFORMATION
sequence and any additional sector addresses and
commands.
The system can monitor DQ3 to determine if the sector erase
timer timed out. (See DQ3: Sector Erase Timer on page 18.)
The time-out begins from the rising edge of the final WE#
pulse in the command sequence.
Once the sector erase operation begins, only the Erase
Suspend command is valid. All other commands are ignored.
The Sector Erase command sequence should be reinitiated
once the device returns to reading array data, to ensure data
integrity.
When the Embedded Erase algorithm is complete, the device
returns to reading array data and addresses are no longer
latched. The system can determine the status of the erase
operation by using DQ7, DQ6, or DQ2. Refer to Write Oper-
ation Status on page 17 for information on these status bits.
Figure 4 illustrates the algorithm for the erase operation.
Refer to the Erase/Program Operations on page 25 for
parameters, and to the Sector Erase Operations Timing
diagram for timing waveforms.
START
Write Erase
Command Sequence
Data Poll
from System
No
Data = FFh?
Embedded
Erase
algorithm
in progress
Yes
Erasure Completed
Note:
1. See the appropriate Command Definitions table for erase
command sequence.
2. See DQ3: Sector Erase Timer on page 18 for more information.
Figure 4. Erase Operation
Erase Suspend/Erase Resume Commands
The Erase Suspend command allows the system to interrupt
a sector erase operation and then read data from, or program
data to, any sector not selected for erasure. This command is
valid only during the sector erase operation, including the 50
µs time-out period during the sector erase command
sequence. The Erase Suspend command is ignored if written
during the chip erase operation or Embedded Program algo-
rithm. Writing the Erase Suspend command during the
Sector Erase time-out immediately terminates the time-out
period and suspends the erase operation. Addresses are
don’t-cares when writing the Erase Suspend command.
When the Erase Suspend command is written during a sector
erase operation, the device requires a maximum of 20 µs to
suspend the erase operation. However, when the Erase
Suspend command is written during the sector erase time-
out, the device immediately terminates the time-out period
and suspends the erase operation.
After the erase operation is suspended, the system can read
array data from or program data to any sector not selected for
erasure. (The device “erase suspends” all sectors selected
for erasure.) Normal read and write timings and command
definitions apply. Reading at any address within erase-sus-
pended sectors produces status data on DQ7–DQ0. The
system can use DQ7, or DQ6 and DQ2 together, to deter-
mine if a sector is actively erasing or is erase-suspended.
See Write Operation Status on page 17 for information on
these status bits.
After an erase-suspended program operation is complete,
the system can once again read array data within non-sus-
pended sectors. The system can determine the status of the
program operation using the DQ7 or DQ6 status bits, just as
in the standard program operation. See Write Operation
Status on page 17 for more information.
The system may also write the autoselect command
sequence when the device is in the Erase Suspend mode.
The device allows reading autoselect codes even at
addresses within erasing sectors, since the codes are not
stored in the memory array. When the device exits the
autoselect mode, the device reverts to the Erase Suspend
mode, and is ready for another valid operation. See
Autoselect Command Sequence on page 13 for more
information.
The system must write the Erase Resume command
(address bits are don’t care) to exit the erase suspend mode
and continue the sector erase operation. Further writes of the
Resume command are ignored. Another Erase Suspend
command can be written after the device resumes erasing.
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Am29F004B
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