AM29F200 datasheet(14/39 Pages) AMD

14 / 39 page

Am29F200B

The system can determine the status of the erase oper-

ation by using DQ7, DQ6, DQ2, or RY/BY#. See “Write

Operation Status” for information on these status bits.

When the Embedded Erase algorithm is complete, 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 Erase/Program Operations tables in “AC

Characteristics” for parameters, and to the Chip/Sector

Erase Operation Timings for timing waveforms.

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

address 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 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

timings 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

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

between 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 recom-

mended 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 Sec tor Erase or E ras e

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 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. Note that a hardware reset during the

sector erase operation immediately terminates the

operation. 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

status of the erase operation by using DQ7, DQ6, DQ2,

or RY/BY#. Refer to “Write Operation Status” for infor-

mation on these status bits.

Figure 3 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

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 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

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-sus-

pended. 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-

a tio n. See “W r ite Operation S tatus ” fo r m o re

information.

The system may also write the autoselect command

sequence when the device is in the Erase Suspend

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