AM29F040B datasheet(14/36 Pages) AMD

14 / 36 page

Am29F040B

21445E5 November 1, 2006

D A TA

SH EE T

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 sta-

tus 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 opera-

tion. 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 Suspend command allows the system to in-

terrupt 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. Ad-

dresses 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 ter-

minates the time-out period and suspends the erase

operation.

After the erase operation has been 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-suspended sec-

tors 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.

After an erase-suspended program operation is com-

plete, the system can once again read array data within

non-suspended sectors. The system can determine

the status of the program operation using the DQ7 or

DQ6 status bits, just as in the standard program oper-

ation. See “Wr ite Op eration Status” fo r 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”

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 de-

vice has resumed erasing.

Notes:

1. See the appropriate Command Definitions table for erase

command sequence.

2. See “DQ3: Sector Erase Timer” for more information.

Figure 2.

Erase Operation

START

Write Erase

Command Sequence

Data Poll

from System

Data = FFh?

Yes

Erasure Completed

Embedded

Erase

algorithm

in progress

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