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AM29LV800DB-120ED Datasheet(PDF) 27 Page - Advanced Micro Devices |
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AM29LV800DB-120ED Datasheet(HTML) 27 Page - Advanced Micro Devices |
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27 / 51 page  January 21, 2005 Am29LV800D_00_A4_E Am29LV800D 25 P R E L I M I NARY DQ5 went high. If the toggle bit is no longer tog- gling, the device has successfully completed the program or erase operation. If it is still toggling, the device did not completed the operation suc- cessfully, and the system must write the reset command to return to reading array data. The remaining scenario is that the system ini- tially 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 (top of Figure 1). DQ5: Exceeded Timing Limits DQ5 indicates whether the program or erase time has exceeded a specified internal pulse count limit. Under these conditions DQ5 pro- duces a “1.” This is a failure condition that indi- cates 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 op era ti on, an d when the opera tion 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 com- mand. 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 com- mands 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# 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 com- plete. If DQ3 is “0”, the device will accept addi- tional sector erase commands. To ensure the command has been accepted, the system soft- ware 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 6 shows the outputs for DQ3. START No Yes Yes DQ5 = 1? No Yes Toggle Bit = Toggle? No Program/Erase Operation Not Complete, Write Reset Command Program/Erase Operation Complete Read DQ7–DQ0 Toggle Bit = Toggle? Read DQ7–DQ0 Twice Read DQ7–DQ0 Notes: 1. Read toggle bit twice to determine whether or not it is toggling. See text. 2. Recheck toggle bit because it may stop toggling as DQ5 changes to “1”. See text. Figure 1. Toggle Bit Algorithm (Notes 1, 2) (Note 1) |
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