AM29F004B datasheet(17/37 Pages) AMD

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8/5/05

Am29F004B

AD VA NC E

IN FO RM AT ION

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.

Note:

See the appropriate Command Definitions table for erase

command sequence.

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.

START

Write Erase

Command Sequence

Data Poll

from System

Data = FFh?

Yes

Erasure Completed

Embedded

Erase

algorithm

in progress

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