AM29BDS640G datasheet(37/77 Pages) AMD

37 / 77 page

May 9, 2006 25903C2

Am29BDS640G

Data

Sheet

The system can monitor DQ3 to determine if the sector erase timer has timed out

(See “DQ3: Sector Erase Timer” section on page 43.). The time-out begins from

the rising edge of the final WE# pulse in the command sequence.

When the Embedded Erase algorithm is complete, the bank returns to reading

array data and addresses are no longer latched. Note that while the Embedded

Erase operation is in progress, the system can read data from the non-erasing

bank. The system can determine the status of the erase operation by reading

DQ7 or DQ6/DQ2 in the erasing bank. Refer to the “Write Operation Status” sec-

tion on page 38 section for information on these status bits.

Once the sector erase operation has begun, only the Erase Suspend command is

valid. All other commands are ignored. However, note that a hardware reset im-

mediately terminates the erase operation. If that occurs, the sector erase

command sequence should be reinitiated once that bank has returned to reading

array data, to ensure data integrity.

The host system may also initiate the sector erase command sequence while the

device is in the unlock bypass mode. The command sequence is four cycles cycles

in length instead of six cycles.

Figure 2 illustrates the algorithm for the erase operation. Refer to the Erase/Pro-

gram Operations table in the AC Characteristics section for parameters and timing

diagrams.

Erase Suspend/Erase Resume Commands

The Erase Suspend command, B0h, allows the system to interrupt a sector erase

operation and then read data from, or program data to, any sector not selected

for erasure. The bank address is required when writing this command. This com-

mand is valid only during the sector erase operation, including the minimum 50

µs time-out period during the sector erase command sequence. The Erase Sus-

pend command is ignored if written during the chip erase operation or Embedded

Program algorithm.

When the Erase Suspend command is written during the sector erase operation,

the device requires a maximum of 35 µs to suspend the erase operation. How-

ever, 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 suspended, the bank enters the erase-sus-

pend-read mode. The system can read data from or program data to any sector

not selected for erasure. (The device “erase suspends” all sectors selected for

erasure.) Reading at any address within erase-suspended sectors produces sta-

tus information 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. Refer

to the Write Operation Status section for information on these status bits.

After an erase-suspended program operation is complete, the bank returns to the

erase-suspend-read mode. The system can determine the status of the program

operation using the DQ7 or DQ6 status bits, just as in the standard program op-

eration. Refer to the “Write Operation Status” section for more information.

In the erase-suspend-read mode, the system can also issue the autoselect com-

mand sequence. Refer to the “Autoselect Functions” section on page 16 and

“Autoselect Command Sequence” section on page 31 sections for details.

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