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19 page 
18 Am29F010B November 18, 2002 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 addi- tional sectors are selected for erasure, the entire time- out also applies after each additional sector erase com- mand. When the time-out is complete, DQ3 switches from “0” to “1.” The system may ignore DQ3 if the sys- tem can guarantee that the time between additional sector erase commands will always be less than 50 µs. 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# Poll- ing) 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 are ignored until the erase operation is complete. If DQ3 is “0”, the device will accept additional sector erase commands. To en- sure 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 com- mand might not have been accepted. Table 5 shows the outputs for DQ3. Table 5. Write Operation Status Notes: 1. DQ7 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: Exceeded Timing Limits” for more information. Operation DQ7 (Note 1) DQ6 DQ5 (Note 2) DQ3 Standard Mode Embedded Program Algorithm DQ7# Toggle 0 N/A Embedded Erase Algorithm 0 Toggle 0 1 Erase Suspend Mode Reading within Erase Suspended Sector 1 No toggle 0 N/A Reading within Non-Erase Suspended Sector Data Data Data Data |
