AM29BDS640G datasheet(44/65 Pages) SPANSION

44 / 65 page

Am29BDS640G

25903C1 October 1, 2003

Prelimin ary

sectors are selected for erasure. Thus, both status bits are required for sector and

mode information. Refer to Table 14 to compare outputs for DQ2 and DQ6.

See the following for additional information: Figure 5, “Toggle Bit Algorithm,” on

page 41, See “DQ6: Toggle Bit I” on page 40., Figure 28, “Toggle Bit Timings

(During Embedded Algorithm),” on page 65, and Table 14, “DQ6 and DQ2 Indi-

cations,” on page 42.

Table 14. DQ6 and DQ2 Indications

Reading Toggle Bits DQ6/DQ2

Refer to Figure 4 for the following discussion. Whenever the system initially be-

gins reading toggle bit status, it must read DQ7–DQ0 at least twice in a row to

determine whether a toggle bit is toggling. Typically, the 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 completed 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 system 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 suc-

cessfully completed the program or erase operation. If it is still toggling, the

device did not completed the operation successfully, and the system must write

the reset command to return to reading array data.

The remaining scenario is that the system initially determines 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, determining the status as de-

scribed 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 algo-

rithm when it returns to determine the status of the operation (top of Figure 4).

DQ5: Exceeded Timing Limits

DQ5 indicates whether the program or erase time has exceeded a specified inter-

nal pulse count limit. Under these conditions DQ5 produces a “1,” indicating that

the program or erase cycle was not successfully completed.

If device is

and the system reads

then DQ6

and DQ2

programming,

at any address,

toggles,

does not toggle.

actively erasing,

at an address within a sector

selected for erasure,

toggles,

also toggles.

at an address within sectors not

selected for erasure,

toggles,

does not toggle.

erase suspended,

at an address within a sector

selected for erasure,

does not toggle,

toggles.

at an address within sectors not

selected for erasure,

returns array data,

returns array data. The system can read

from any sector not selected for erasure.

programming in

erase suspend

at any address,

toggles,

is not applicable.

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