AM29BDS128H datasheet(53/89 Pages) SPANSION

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May 10, 2006 27024B3

Am29BDS128H/Am29BDS640H

D A TA

SH EE T

Table 22.

DQ6 and DQ2 Indications

Reading Toggle Bits DQ6/DQ2

Refer to Figure 9, “Toggle Bit Algorithm,” on page 50 for

the following discussion. Whenever 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, 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 tog-

gling, 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 tog-

gling 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 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 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

determine the status of the operation (Figure 9, “Toggle

Bit Algorithm,” on page 50).

DQ5: Exceeded Timing Limits

DQ5 indicates whether the program or erase time has

exceeded a specified internal pulse count limit. Under

these conditions DQ5 produces a “1,” indicating that

the program or erase cycle was not successfully com-

pleted.

The device may output a “1” on DQ5 if the system tries

to program a “1” to a location that was previously pro-

grammed 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 determine 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 assumed to

be less than tSEA, the system need not monitor DQ3.

See also “Sector Erase Command Sequence” on

page 38.

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

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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