12

The Autoselect mode also facilitates the determination of sector group protection in the system. By performing

desired sector group address, the device will return 01h for a protected sector group and 00h for a non-protected

sector group.

Write

Device erasure and programming are accomplished via the command register. The contents of the register serve

as inputs to the internal state machine. The state machine outputs dictate the function of the device.

The command register itself does not occupy any addressable memory location. The register is a latch used to

store the commands, along with the address and data information needed to execute the command. The

the falling edge of WE or CE, whichever happens later; while data is latched on the rising edge of WE or CE,

whichever happens first. Standard microprocessor write timings are used.

Refer to AC Write Characteristics and the Erase/Programming Waveforms for specific timing parameters.

Sector Group Protection

The MBM29F080A features hardware sector group protection. This feature will disable both program and erase

operations in any combination of eight sector groups of memory. Each sector group consists of four adjacent

sectors grouped in the following pattern: sectors

Group Address Table” in “sFLEXIBLE SECTOR-ERASE ARCHITECTURE”). The sector group protection feature

is enabled using programming equipment at the user's site. The device is shipped with all sector groups

unprotected.

“Sector Address Table” and “Sector Group Address Table” in “sFLEXIBLE SECTOR-ERASE ARCHITECTURE”

define the sector address for each of the thirty two (16) individual sectors, and the sector group address for each

of the eight (8) individual group sectors. Programming of the protection circuitry begins on the falling edge of

the WE pulse and is terminated with the rising edge of the same. Sector addresses must be held constant during

the WE pulse. See “Temporary Sector Group Unprotection Timing Diagram” in “sTIMING DIAGRAM” and

“Temporary Sector Group Unprotection Algorithm” in “sFLOW CHART” for sector protection waveforms and

algorithm.

It is also possible to determine if a sector group is protected in the system by writing an Autoselect command.

“MBM29F080A Sector Protection Verify Autoselect Codes Table” in “sFLEXIBLE SECTOR-ERASE ARCHITEC-

TURE” for Autoselect codes.

Temporary Sector Group Unprotection

This feature allows temporary unprotection of previously protected sector groups of the MBM29F080A device

in order to change data. The Sector Group Unprotection mode is activated by setting the RESET pin to high

voltage (12 V). During this mode, formerly protected sector groups can be programmed or erased by selecting

the sector group addresses. Once the 12 V is taken away from the RESET pin, all the previously protected sector