FLASH
AS29F040
Austin Semiconductor, Inc.
including the 50µs 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
algorithm. Writing the Erase Suspect 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 Suspect command.
When the Erase Suspect command is written during a
sector erase operation, the device requires a maximum of 20µs
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 has been suspected, the system
can read array data from 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-suspended sectors
produces status data on DQ7-DQ0. The system can use DQ7,
or DQ6 and DQ2 together, to determine if a sector is actively
erasing or is erase-suspended. See “Write Operation Status”
for information on these status bits.
Sector Erase Command Sequence
Sector erase is a six bus cycle operation. The sector erase
command sequence is initiated by writing two unlock cycles,
followed by a set-up command. Two additional unlock write
cycles are then followed by the addresss of the sector to be
erased, and the sector erase command. The Command
Definitions table shows the address and data requirements for
the sector erase command sequence.
The device does not require the system to preprogram the
memory prior to erase. The Embedded Erase algorithm
automatically programs and verifies the sector for an all zero
data pattern prior to electrical erase. The system is not required
to provide any controls or timings during these operations.
After the command sequence is written, a sector erase
time-out of 50µs begins. During the time-out period, additional
sector addresses and sector erase commands may be written.
Loading the sector erase buffer may be done in any sequence,
and the number of sectors may be from one sector to all sectors.
The time between these additional cycles must be less than
50µs, otherwise the last address and command might not be
accepted, and erasure may begin. It is recommended that
processor interrupts be disabled during this time to ensure all
commands are accepted. The interrupts can be re-enabled after
the last Sector Erase command is written. If the time between
additional sector erase commands can be assumed to be less
than 50µs, the system need not monitor DQ3. Any command
other than Sector Erase or Erase Suspend during the time-out
period resets the device to reading array data. The system
must rewrite the command sequence and any additional sector
addresses and commands.
FIGURE 2: ERASE OPERATION
The system can monitor DQ3 to determine if the sector
erase timer has timed out. (See the “DQ3: Sector Erase Timer”
section.) The time-out begins from the rising edge of the final
WE\ pulse in the command sequence.
Once the sector erase operation has begun, only the Erase
Suspend command is valid. All other commands are ignored.
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
Operation Status” for information on these status bits.
Figure 2 illustrates the algorithm for the erase operation.
Refer to the Erase/Program Operations tables in the “AC
Characteristics” section for parameters, and to the Sector Erase
Operations Timing diagram for timing waveforms.
Erase Suspend/Erase Resume Commands
The Erase Suspect 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,
NOTE:
1) See the appropriate Command Definitions table for program
command sequence.
2) See “DQ3: Sector Erase Timer” for more information.
AS29F040
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Rev. 2.2 09/07
8
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