AM29LV002 datasheet(13/34 Pages) AMD

13 / 34 page

Am29LV002

PR EL I M I NAR Y

Chip Erase Command Sequence

Chip erase is a six bus cycle operation. The chip 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 chip erase

command, which in turn invokes the Embedded Erase

algorithm. The device does

not require the system to

preprogram prior to erase. The Embedded Erase algo-

rithm automatically preprograms and verifies the entire

memory for an all zero data pattern prior to electrical

erase. The system is not required to provide any con-

trols or timings during these operations. Table 5 shows

the address and data requirements for the chip erase

command sequence.

Any commands written to the chip during the Embed-

ded Erase algorithm are ignored. Note that a hardware

reset during the chip erase operation immediately ter-

minates the operation. The Chip Erase command se-

quence should be reinitiated once the device has

returned to reading array data, to ensure data integrity.

The system can determine the status of the erase op-

eration by using DQ7, DQ6, DQ2, or RY/BY#. See

“Write Operation Status” for information on these sta-

tus bits. When the Embedded Erase algorithm is com-

plete, the device returns to reading array data and

addresses are no longer latched.

Figure 3 illustrates the algorithm for the erase opera-

tion. See the Read Operations tables in “AC Character-

istics” for parameters, and to Figure 15 for timing

diagrams.

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 ad-

ditional unlock write cycles are then followed by the ad-

dress of the sector to be erased, and the sector erase

command. Table 5 shows the address and data re-

quirements for the sector erase command sequence.

The device does

not require the system to preprogram

the memory prior to erase. The Embedded Erase algo-

rithm 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 tim-

ings during these operations.

After the command sequence is written, a sector erase

time-out of 50 µs begins. During the time-out period,

additional sector addresses and sector erase com-

mands may be written. Loading the sector erase buffer

may be done in any sequence, and the number of sec-

tors may be from one sector to all sectors. The time be-

tween these additional cycles must be less than 50 µs,

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 50 µs, 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.

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 ris-

ing edge of the final WE# pulse in the command se-

quence.

Once the sector erase operation has begun, only the

Erase Suspend command is valid. All other commands

are ignored. Note that a hardware reset during the

sector erase operation immediately terminates the op-

eration. The Sector Erase command sequence should

be reinitiated once the device has returned 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 sta-

tus of the erase operation by using DQ7, DQ6, DQ2, or

RY/BY#. (Refer to “Write Operation Status” for informa-

tion on these status bits.)

Figure 3 illustrates the algorithm for the erase opera-

tion. Refer to the Read Operations tables in the “AC

Characteristics” section for parameters, and to Figure

15 for timing diagrams.

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 time-out period 50 µs

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 Sus-

pend 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

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