MBM29PL64LM datasheet(23/69 Pages) SPANSION

23 / 69 page

MBM29PL64LM90/10

Temporary Sector Group Unprotection

This feature allows temporary unprotection of previously protected sector groups of the devices in order to change

data. The Sector Group Unprotection mode is activated by setting the RESET pin to high voltage (VID). During

this mode, formerly protected sector groups can be programmed or erased by selecting the sector group ad-

dresses. Once the VID is taken away from the RESET pin, all the previously protected sector groups will be

protected again. Refer to “Temporary Sector Group Unprotection Timing Diagram” in sTIMING DIAGRAM and

“Temporary Sector Group Unprotection Algorithm” in sFLOW CHART.

Hardware Reset

The devices may be reset by driving the RESET pin to VIL from VIH. The RESET pin has a pulse requirement

and has to be kept low (VIL) for at least “tRP” 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

“tREADY” 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.

Write Protect (WP)

The Write Protection function provides a hardware method of protecting certain first 64K bytes words sectors

without using VID. This function is one of two provided by the WP/ACC pin.

If the system asserts VIL on the WP/ACC pin, the device disables program and erase functions in the first

64K bytes / 32K words sectors independently of whether this sector was protected or unprotected using the

method described in “Sector Group Protection" above.

If the system asserts VIH on the WP/ACC pin, the device reverts of whether the outermost 8K bytes / 4K words

sectors were last set to be protected to the unprotected status. Sector protection or unprotection for this sector

depends on whether this was last protected or unprotected using the method described in “Sector protection/

unprotection”.

Accelerated Program Operation

The device offers accelerated program operation which enables programming in high speed. If the system asserts

VACC to the WP/ACC pin, the device automatically enters the acceleration mode and the time required for program

operation will reduce to about 85%. This function is primarily intended to allow high speed programing, so caution

is needed as the sector group becomes temporarily unprotected.

The system would use a fast program command sequence when programming during acceleration mode. Set

command to fast mode and reset command from fast mode are not necessary. When the device enters the

acceleration mode, the device is automatically set to fast mode. Therefore, the present sequence could be used

for programming and detection of completion during acceleration mode.

Removing VACC from the WP/ACC pin returns the device to normal operation. Do not remove VACC from the WP/

ACC pin while programming. See “Accelerated Program Timing Diagram” in sTIMING DIAGRAM.

Enhanced VCCQ Feature

The output voltage generated on the device is determined based on the VCCQ level. This feature allows the device

to operate in mixed-voltage environments, driving and receiving signals to and from other devices on the same

bus.

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