MBM29F800TA-55/-70/-90/MBM29F800BA-55/-70/-90
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
device requires time of tRH before it will allow read access. When the RESET pin is low, the device 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. Refer to “RESET/RY/BY Timing
Diagram” in ■ TIMING DIAGRAM for the timing diagram. Refer to “Temporary Sector Unprotection” in
■ FUNCTIONAL DESCRIPTION for additional functionality.
If hardware reset occurs during Embedded Erase Algorithm, there is a possibility that the erasing sector(s)
cannot be used.
Byte/Word Configuration
The BYTE pin selects the byte (8-bit) mode or word (16-bit) mode for the MBM29F800TA/BA device. When this
pin is driven high, the device operates in the word (16-bit) mode. The data is read and programmed at DQ15 to
DQ0. When this pin is driven low, the device operates in byte (8-bit) mode. Under this mode, the DQ15/A-1 pin
becomes the lowest address bit and DQ14 to DQ8 bits are tri-stated. However, the command bus cycle is always
an 8-bit operation and hence commands are written at DQ7 to DQ0 and the DQ15 to DQ8 bits are ignored. Refer
to “Timing Diagram for Word Mode Configuration”, “Timing Diagram for Byte Mode Configuration” and “BYTE
Timing Diagram for Write Operations” in ■ TIMING DIAGRAM for the timing diagram.
Data Protection
The MBM29F800TA/BA are designed to offer protection against accidental erasure or programming caused by
spurious system level signals that may exist during power transitions. During power up the device automatically
resets the internal state machine in the read mode. Also, with its control register architecture, alteration of the
memory contents only occurs after successful completion of specific multi-bus cycle command sequences.
The device also incorporate several features to prevent inadvertent write cycles resulting form VCC power-up and
power-down transitions or system noise.
Low VCC Write Inhibit
To avoid initiation of a write cycle during VCC power-up and power-down, a write cycle is locked out for VCC less
than 3.2 V (typically 3.7 V). If VCC < VLKO, the command register is disabled and all internal program/erase circuits
are disabled. Under this condition the device will reset to the read mode. Subsequent writes will be ignored until
the VCC level is greater than VLKO. It is the users responsibility to ensure that the control pins are logically correct
to prevent unintentional writes when VCC is above 3.2 V.
If Embedded Erase Algorithm is interrupted, there is possibility that the erasing sector(s) cannot be used.
Write Pulse “Glitch” Protection
Noise pulses of less than 5 ns (typical) on OE, CE, or WE will not initiate a write cycle.
Logical Inhibit
Writing is inhibited by holding any one of OE = VIL, CE = VIH, or WE = VIH. To initiate a write cycle CE and WE
must be a logical zero while OE is a logical one.
Power-Up Write Inhibit
Power-up of the device with WE = CE = VIL and OE = VIH will not accept commands on the rising edge of WE.
The internal state machine is automatically reset to the read mode on power-up.
Sector Protection
Device user is able to protect each sector individually to store and protect data.
Protection circuit voids both write and erase commands that are addressed to protected sectors.
Any commands to write or erase addressed to protected sector are ignore. Refer to “Sector Protection” in
■ FUNCTIONAL DESCRIPTION.
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