AM29BDS640G Datasheet, PDF (45/78 Pages) SPANSION – 64 Megabit (4 M x 16-Bit) CMOS 1.8 Volt-only Simultaneous Read/Write, Burst Mode Flash Memory

Preliminary
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
Standard
Mode
Status
Embedded Program Algorithm
Embedded Erase Algorithm
DQ7
(Note 2)
DQ7#
0
DQ6
Toggle
Toggle
DQ5
(Note 1)
0
0
DQ3
N/A
1
DQ2
(Note 2)
No toggle
Toggle
Erase
Suspend
Mode
Erase-Suspend-
Read (Note 4)
Erase
Suspended Sector
Non-Erase Suspended
Sector
1
Data
No toggle
Data
0
Data
N/A
Data
Toggle
Data
Erase-Suspend-Program
DQ7#
Toggle
0
N/A
N/A
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.
October 1, 2003 25903C1
Am29BDS640G
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