MBM29F080A datasheet(20/44 Pages) SPANSION

20 / 44 page

MBM29F080A-55/-70/-90

During programming, the RY/BY pin is driven low after the rising edge of the fourth WE pulse. During an erase

operation, the RY/BY pin is driven low after the rising edge of the sixth WE pulse. The RY/BY pin will indicate a

busy condition during RESET pulse. Refer to “RY/BY Timing Diagram during Program/Erase Operations” in

“sTIMING DIAGRAM” for a detailed timing diagram. The RY/BY pin is pulled high in standby mode.

Since this is an open-drain output, several RY/BY pins can be tied together in parallel with a pull-up resistor to VCC.

RESET

Hardware Reset

The MBM29F080A device may be reset by driving the RESET pin to VIL. The RESET pin must be kept low (VIL)

for at least 500 ns. Any operation in progress will be terminated and the internal state machine will be reset to

the read mode 20

µs after the RESET pin is driven low. If a hardware reset occurs during a program operation,

the data at that particular location will be indeterminate.

When the RESET pin is low and the internal reset is complete, the device goes to standby mode and cannot be

accessed. Also, note that all the data output pins are tri-stated for the duration of the RESET pulse. Once the

RESET pin is taken high, the device requires tRH of wake up time until outputs are valid for read access.

The RESET pin may be tied to the system reset input. Therefore, if a system reset occurs during the Embedded

Program or Erase Algorithm, the device will be automatically reset to read mode and this will enable the system’s

microprocessor to read the boot-up firmware from the Flash memory.

Data Protection

The MBM29F080A is 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 completions of specific multi-bus cycle command sequences.

The device also incorporates several features to prevent inadvertent write cycles resulting from 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.

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.

MBM29F080A Scheda tecnica(PDF) 20 Page - SPANSION