MBM29LV400TC-55/70/90/MBM29LV400BC-55/70/90
8. Temporary Sector Unprotection
This feature allows temporary unprotection of previously protected sectors of the MBM29LV400TC/BC devices
in order to change data. The Sector Unprotection mode is activated by setting the RESET pin to high voltage
(12 V). During this mode, formerly protected sectors can be programmed or erased by selecting the sector
addresses. Once the 12 V is taken away from the RESETpin, all the previously protected sectors will be protected
again. See “14. Temporary Sector Unprotection Timing Diagram” in ■TIMING DIAGRAM and “6. Temporary
Sector Unprotection Algorithm” in ■FLOW CHART.
9. RESET
Hardware Reset
The MBM29LV400TC/BC devices may be reset by driving the RESET pin to VIL. The RESET pin has a pulse
requirement and has to be kept low (VIL) for at least 500 ns in order to properly reset the internal state machine.
Any operation in the process of being executed will be terminated and the internal state machine will be reset
to the read mode 20 µs after the RESET pin is driven low. Furthermore, once the RESET pin goes high, the
devices require an additional tRH before it will allow read access. When the RESET pin is low, the devices will
be in the standby mode for the duration of the pulse and all the data output pins will be tri-stated. If a hardware
reset occurs during a program or erase operation, the data at that particular location will be corrupted. Please
note that the RY/BY output signal should be ignored during the RESET pulse. See “9. RESET/RY/BY Timing
Diagram” in ■TIMING DIAGRAM for the timing diagram. Refer to “8. Temporary Sector Unprotection” for
additional functionality.
If hardware reset occurs during Embedded Erase Algorithm, there is a possibility that the erasing sector(s)
cannot be used.
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SPANSION [ SPANSION ]
