FLASH

AS29F040

Micross Components reserves the right to change products or specifications without notice.

12

AS29F040

Rev. 2.3 01/10

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 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.

The remaining scenario is that the system initially

determines that the toggle bit it 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 (top of Figure 4).

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.” This is a failure condition

that indicates the program or erase cycle was not successfully

completed.

The DQ5 failure condition may appear if the system tries

to program a “1” to a location that is previously programmed 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 operation has exceeded the timing limits, DQ5 produces a

“1.”

Under both these conditions, the system must issue the

reset command to return the device to reading array data.

DQ3: Sector Erase Timer

After writing a sector erase command sequence, the

system may read DQ3 to determine whether or not an erase

operation 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 is complete, DQ3

switches from “0” to “1.” The system may ignore DQ3 if the

system can guarantee that the time between additional sector

erase commands will always be less than 50μs. See also the

“Sector Erase Command Sequence” section.

After the sector erase command sequence is written, the

system should read the status on DQ7 (Data\ Polling) or DQ6

(Toggle Bit I) to ensure the device has accepted the command

sequence, and then read DQ3. If DQ3 is “1”, the internally

controlled erase cycle has begun; all further commands (other

than Erase Suspend) are ignored until the erase operation is

complete. If DQ3 is “0”, the device will accept additional sector

erase commands. To ensure the command has been accepted,

the system software should check the status of DQ3 prior to

and following each subsequent sector erase command. If DQ3

is high on the second status check, the last command might not

have been accepted. Table 5 shows the outputs for DQ3.

TABLE 5: WRITE OPERATION STATUS

NOTES:

1. DQ7 and DQ2 requires a valid address when reading status information. Refer to the appropriate subsection for further details.

2. DQ5 switches to ‘1’ when an Embedded Program or Embedded Erase operation has exceeded the maximum timing limits. See “DQ5: Exceeding Timing

Limits” for more information.

DQ7

1

DQ6

DQ5

2

DQ3

DQ2

1

Embedded Program Algorithm

DQ7\

Toggle

0

0

No Toggle

Embedded Erase Algorithm

0

Toggle

0

1

Toggle

Reading within Erase Suspended Sector

1

No toggle

0

N/A

Toggle

Reading within Non-Erase Suspended Sector

Data

Data

Data

Data

Data

Erase-Suspend-Program

DQ7\

Toggle

0

N/A

N/A

Standard

Mode

OPERATION

Erase

Suspend

Mode