AS29F400
Preliminary information
®
Status operations
Only active during automated on-chip algorithms or sector erase time outs. DQ7 reflects
complement of data last written when read during the automated on-chip algorithm (0 during
erase algorithm); reflects true data when read after completion of an automated on-chip algorithm
(1 after completion of erase agorithm).
DATA polling (DQ7)
Active during automated on-chip algorithms or sector time outs. DQ6 toggles when CE or OE
toggles, or an Erase Resume command is invoked. DQ6 is valid after the rising edge of the fourth
pulse of WE during programming; after the rising edge of the sixth WE pulse during chip erase;
after the last rising edge of the sector erase WE pulse for sector erase. For protected sectors,
DQ6 toggles for <1 µs during writes, and <5 µs during erase (if all selected sectors are protected);
in both cases, data is unaffected.
Toggle bit 1 (DQ6)
Indicates unsuccessful completion of program/erase operation (DQ5 = 1). DATA polling remains
active; CE powers the device down to 2 mA. If DQ5 = 1 during chip erase, all or some sectors are
defective; during sector erase, the sector is defective (in this case, reset the device and execute a
program or erase command sequence to continue working with functional sectors); during byte
programming, that particular byte is defective. Attempting to program 0 to 1 will set DQ5 = 1.
Exceeding time limit
(DQ5)
Checks whether sector erase timer window is open. If DQ3 = 1, erase is in progress; no commands
will be accepted. If DQ3 = 0, the device will accept sector erase commands. Check DQ3 before and
after each Sector Erase command to verify that the command was accepted.
Sector erase timer
(DQ3)
During sector erase, DQ2 toggles with OE or CE only during an attempt to read a sector being
erased. During chip erase, DQ2 toggles with OE or CE for all addresses. If DQ5 = 1, DQ2 toggles
only at sector addresses where failure occurred, and will not toggle at other sector addresses. Use
DQ2 in conjunction with DQ6 to determine whether device is in auto erase or erase suspend
mode.
Toggle bit 2 (DQ2)
Write operation status
Status
DQ7
DQ6
DQ5
0
DQ3
0
DQ2
RY/BY
Auto programming (byte/word) DQ7
Toggle
Toggle
No toggle
No toggle
0
0
1
†
Program/erase in auto erase
Read erasing sector
0
1
0
1
Toggle
0
0
Toggle
In progress
Erase
suspend
mode
Read non-erasing
sector
Data
DQ7
Data
Data
0
Data
0
Data
1
0
Program in erase
suspend
†
Toggle
Toggle
Auto programming (byte/word) DQ7
Toggle
Toggle
Toggle
1
1
1
0
1
0
No toggle
0
0
0
‡
Exceeded time limits
Program/erase in auto erase
Program in erase suspend
0
Toggle
‡
DQ7
Toggle
†
Toggles with OE or CE only for erasing or erase suspended sector addresses.
‡
Toggles only if DQ5 = 1 and address applied is within sector that exceeded timing limits.
DQ8–DQ15 = Don’t care in ×16 mode.
8
ALSC [ ALLIANCE SEMICONDUCTOR CORPORATION ]
