S71PL254 datasheet(79/196 Pages) SPANSION

79 / 196 page

August 12, 2004 S29PL127J_064J_032J_MCP_00_A3

S29PL127J/S29PL064J/S29PL032J for MCP

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I n f o rmatio n

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 7).

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.

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

location that was previously programmed to “0.” Only an erase operation can

change a “0” back to a “1.” Under this condition, the device halts the opera-

tion, 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 de-

termine 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.” See also

the Sector Erase Command Sequence.

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 device will accept addi-

tional sector erase commands. To ensure the command has been accepted, the

system software should check the status of DQ3 prior to and following each sub-

sequent sector erase command. If DQ3 is high on the second status check, the

last command might not have been accepted.

Table 19 shows the status of DQ3 relative to the other status bits.

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