AM29BDS640G datasheet(45/77 Pages) AMD

45 / 77 page

May 9, 2006 25903C2

Am29BDS640G

Data

Sheet

The device may output a “1” on DQ5 if the system tries to program a “1” to a

location that was previously programmed to “0.” Only an erase operation can

change a “0” back to a “1.” Under this condition, the device halts the operation,

and when the timing limit has been exceeded, DQ5 produces a “1.”

Under both these conditions, the system must write the reset command to return

to the read mode (or to the erase-suspend-read mode if a bank was previously

in the erase-suspend-program mode).

DQ3: Sector Erase Timer

After writing a sector erase command sequence, the system may read DQ3 to de-

termine whether or not erasure has begun. (The sector erase timer does not

apply to the chip erase command.) If additional sectors are selected for erasure,

the entire time-out also applies after each additional sector erase command.

When the time-out period is complete, DQ3 switches from a “0” to a “1.” If the

time between additional sector erase commands from the system can be as-

sumed to be less than 50 µs, the system need not monitor DQ3. See also the

Sector Erase Command Sequence section.

After the sector erase command is written, the system should read the status of

DQ7 (Data# Polling) or DQ6 (Toggle Bit I) to ensure that the device has accepted

the command sequence, and then read DQ3. If DQ3 is “1,” the Embedded Erase

algorithm has begun; all further commands (except Erase Suspend) are ignored

until the erase operation is complete. If DQ3 is “0,” the device will accept addi-

tional sector erase commands. To ensure the command has been accepted, the

system software should check the status of DQ3 prior to and following each sub-

sequent sector erase command. If DQ3 is high on the second status check, the

last command might not have been accepted.

Table 15 shows the status of DQ3 relative to the other status bits.

Table 15. Write Operation Status

Notes:

1. DQ5 switches to ‘1’ when an Embedded Program or Embedded Erase operation has exceeded the maximum timing

limits. Refer to the section on DQ5 for more information.

2. DQ7 and DQ2 require a valid address when reading status information. Refer to the appropriate subsection for

further details.

3. When reading write operation status bits, the system must always provide the bank address where the Embedded

Algorithm is in progress. The device outputs array data if the system addresses a non-busy bank.

4. The system may read either asynchronously or synchronously (burst) while in erase suspend. RDY will function ex-

actly as in non-erase-suspended mode.

Status

DQ7

(Note 2)

DQ6

DQ5

(Note 1)

DQ3

DQ2

(Note 2)

Standard

Mode

Embedded Program Algorithm

DQ7#

Toggle

N/A

No toggle

Embedded Erase Algorithm

Toggle

Erase

Suspend

Mode

Erase-Suspend-

Read (Note 4)

Erase

Suspended Sector

1No toggle

N/A

Toggle

Non-EraseSuspended

Sector

Data

Erase-Suspend-Program

DQ7#

Toggle

N/A

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