AMD29F010B Datasheet, PDF (17/34 Pages) Advanced Micro Devices – 1 Megabit (128 K x 8-bit) CMOS 5.0 Volt-only, Uniform Sector Flash Memory

DQ6: Toggle Bit I
Toggle Bit I on DQ6 indicates whether an Embedded
Program or Erase algorithm is in progress or complete.
Toggle Bit I may be read at any address, and is valid
after the rising edge of the final WE# pulse in the com-
mand sequence (prior to the program or erase
operation), and during the sector erase time-out.
During an Embedded Program or Erase algorithm op-
eration, successive read cycles to any address cause
DQ6 to toggle. (The system may use either OE# or
CE# to control the read cycles.) When the operation is
complete, DQ6 stops toggling.
After an erase command sequence is written, if all sec-
tors selected for erasing are protected, DQ6 toggles for
approximately 100 µs, then returns to reading array
data. If not all selected sectors are protected, the Em-
bedded Erase algorithm erases the unprotected
sectors, and ignores the selected sectors that are
protected.
If a program address falls within a protected sector,
DQ6 toggles for approximately 2 µs after the program
command sequence is written, then returns to reading
array data.
The Write Operation Status table shows the outputs for
Toggle Bit I on DQ6. Refer to Figure 4 for the toggle bit
algorithm, and to the Toggle Bit Timings figure in the
“AC Characteristics” section for the timing diagram.
Reading Toggle Bit DQ6
Refer to Figure 4 for the following discussion. When-
ever the system initially begins reading toggle bit
status, it must read DQ7–DQ0 at least twice in a row to
determine whether a toggle bit is toggling. Typically, a
system would note and store the value of the toggle bit
after the first read. After the second read, the system
would compare the new value of the toggle bit with the
first. If the toggle bit is not toggling, the device has com-
pleted the program or erase operation. The system can
read array data on DQ7–DQ0 on the following read
cycle.
However, if after the initial two read cycles, the system
determines that the toggle bit is still toggling, the sys-
tem also should note whether the value of DQ5 is high
(see the section on DQ5). If it is, the system should
then determine again whether the toggle bit is toggling,
since the toggle bit may have stopped toggling just as
DQ5 went high. If the toggle bit is no longer toggling,
the device has successfully completed the program or
erase operation. If it is still toggling, the device did not
complete the operation successfully, and the system
must write the reset command to return to reading
array data.
START
Read DQ7–DQ0
Read DQ7–DQ0 (Note 1)
Toggle Bit
No
= Toggle?
Yes
No
DQ5 = 1?
Yes
Read DQ7–DQ0 (Notes
Twice
1, 2)
Toggle Bit
No
= Toggle?
Yes
Program/Erase
Operation Not
Complete, Write
Reset Command
Program/Erase
Operation Complete
Notes:
1. Read toggle bit twice to determine whether or not it is
toggling. See text.
2. Recheck toggle bit because it may stop toggling as DQ5
changes to “1”. See text.
Figure 4. Toggle Bit Algorithm
The remaining scenario is that the system initially de-
termines that the toggle bit is toggling and DQ5 has not
gone high. The system may continue to monitor the
toggle bit and DQ5 through successive read cycles, de-
termining the status as described in the previous
paragraph. Alternatively, it may choose to perform
other system tasks. In this case, the system must start
at the beginning of the algorithm when it returns to de-
termine the status of the operation (top of Figure 4).
Am29F010B
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