Timing Limit Excess Flag (Dq5) - Fujitsu MB90480 Series Hardware Manual

CHAPTER 23 2M/3M BIT FLASH MEMORY

23.5.3 Timing Limit Excess Flag (DQ5)

The timing limit excess flag (DQ5) is used to indicate when the execution of the
automatic algorithm exceeds the time (internal pulse count) specified in the internal
flash memory.
■
State transitions of the timing limit excess flag (DQ5)
❍ State transitions in normal operation
Write
Operation
→
operation
state
completed
→
DQ5 0 DATA: 5
❍ State transitions in operation error mode
Operation Write
state operation
DQ5 1
■
Write/chip sector erase operation
When a read access is performed after a writing operation occurs or the chip sector erase
automatic algorithm starts, "0" is output if the specified time (for write/erase operations) is not
exceeded, while "1" is output if this time is exceeded. This operation is independent of whether
the automatic algorithm is being executed or has ended, thus allowing whether a failure has
occurred during a write/erase operation to be determined. If this flag indicates "1" while the
automatic algorithm is still being executed according to the data polling function or toggle bit
function, it can be assumed that a failure during a write operation has occurred.
For example, if there is an attempt to write "1" to a flash memory address whose corresponding
value has already been set to "0", a failure occurs. In this case, the flash memory will be locked,
and the automatic algorithm will not end. Occasionally, it is likely to end normally as be able to
be written"1". As a result, the data polling flag (DQ7) will output that there is no valid data. The
toggle bit flag (DQ6) will continue with the toggle operation until the time limit is exceeded, and
the timing limit excess flag (DQ5) will output "1". This indicates that the flash memory is not
defective, but was used incorrectly. If this state occurs, execute the reset command.
492
Chip sector Sector
→
erase wait
erase
→
completed start
→
0 1 0
Chip sector
erase
operation
1
Sector erase
→
Sector erase
suspend
erase suspend
resume
(sector being
(sector being
erased)
erased)
0
Sector erased
→
Suspend mode
Sector not being
erased
0 DATA: 5