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MX29F022BPC-90 Datasheet(PDF) 11 Page - Macronix International |
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MX29F022BPC-90 Datasheet(HTML) 11 Page - Macronix International |
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11 / 46 page  11 P/N:PM0556 REV. 1.3, NOV. 11, 2002 MX29F022/022NT/B Q2:Toggle Bit II The "Toggle Bit II" on Q2, when used with Q6, indicates whether a particular sector is actively erasing (that is, the Automatic Erase algorithm is in process), or whether that sector is erase-suspended. Toggle Bit I is valid after the rising edge of the final WE pulse in the command sequence. Q2 toggles when the system reads at addresses within those sectors that have been selected for erasure. (The system may use either OE or CE to control the read cycles.) But Q2 cannot distinguish whether the sector is actively erasing or is erase-suspended. Q6, by com- parison, indicates whether the device is actively eras- ing, or is in Erase Suspend, but cannot distinguish which sectors are selected for erasure. Thus, both status bits are required for sectors and mode information. Refer to Table 4 to compare outputs for Q2 and Q6. Reading Toggle Bits Q6/ Q2 Refer to the toggle bit algorithm for the following discussion. Whenever the system initially begins reading toggle bit status, it must read Q7-Q0 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 toggling, the device has completed the program or erase operation. The system can read array data on Q7-Q0 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 Q5 is high (see the section on Q5). 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 Q5 went high. If the toggle bit is no longer toggling, the device has successfully completed the program or erase opera- tion. 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 system initially determines that the toggle bit is toggling and Q5 has not gone high. The system may continue to monitor the toggle bit and Q5 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 the toggle bit algorithm flow chart). Q5 Exceeded Timing Limits Q5 will indicate if the program or erase time has exceeded the specified limits (internal pulse count). Under these conditions Q5 will produce a "1".This time-out con- dition indicates that the program or erase cycle was not successfully completed. Data Polling and Toggle Bit are the only operating functions not of the device under this condition. If this time-out condition occurs during sector erase operation, it specifies that a particular sector is bad and it may not be reused. However, other sectors are still functional and may be used for the program or erase operation. The device must be reset to use other sectors. Write the Reset command sequence to the de- vice, and then execute program or erase command se- quence. This allows the system to continue to use the other active sectors in the device. If this time-out condition occurs during the chip erase operation, it specifies that the entire chip is bad or combination of sectors are bad. If this time-out condition occurs during the byte programming operation, it specifies that the entire sector containing that byte is bad and this sector may not be reused, (other sectors are still functional and can be reused). The time-out condition may also appear if a user tries to program a non blank location without erasing. In this case the device locks out and never completes the Automatic Algorithm operation. Hence, the system never reads a valid data on Q7 bit and Q6 never stops toggling. Once the Device has exceeded timing limits, the Q5 bit will indicate a "1". Please note that this is not a device failure condition since the device was incorrectly used. |
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