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Temporary Sector Group Unprotection

This feature allows temporary unprotection of previously protected sector groups of the MBM29F016A 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

groups will be protected again. Refer to “Temporary Sector Group Unprotection Timing Diagram” in “s TIMING

DIAGRAM” and “Temporary Sector Group Unprotection Algorithm” in “s FLOW CHART”.

Command Definitions

Device operations are selected by writing specific address and data sequences into the command register.

Writing incorrect address and data values or writing them in the improper sequence will reset the device to the

read mode. “MBM29F016A Command Definitions Table” in “s FLEXIBLE SECTOR-ERASE ARCHITECTURE”

defines the valid register command sequences. Note that the Erase Suspend (B0h) and Erase Resume (30h)

commands are valid only while the Sector Erase operation is in progress. Moreover, both Read/Reset commands

are functionally equivalent, resetting the device to the read mode.

Read/Reset Command

The read or reset operation is initiated by writing the read/reset command sequence into the command register.

Microprocessor read cycles retrieve array data from the memory. The device remains enabled for reads until the

command register contents are altered.

The device will automatically power-up in the read/reset state. In this case, a command sequence is not required

to read data. Standard microprocessor read cycles will retrieve array data. This default value ensures that no

spurious alteration of the memory content occurs during the power transition. Refer to the AC Read

Characteristics and Waveforms for the specific timing parameters.

Autoselect Command

Flash memories are intended for use in applications where the local CPU alters memory contents. As such,

manufacture and device codes must be accessible while the device resides in the target system. PROM

voltage onto the address lines is not generally desirable system design practice.

The device contains an autoselect command operation to supplement traditional PROM programming

methodology. The operation is initiated by writing the autoselect command sequence into the command register.

Following the command write, a read cycle from address XX00h retrieves the manufacture code of 04h. A read

cycle from address XX01h returns the device code ADh. (See “MBM29F016A Sector Protection Verify Autoselect

Codes Table” in “s FLEXIBLE SECTOR-ERASE ARCHITECTURE”).

Sector state (protection or unprotection) will be informed by address XX02h.

To terminate the operation, it is necessary to write the read/reset command sequence into the register and also

to write the Autoselect command during the operation, execute it after writing Read/Reset command sequence.

Byte Programming

The device is programmed on a byte-by-byte basis. Programming is a four bus cycle operation. There are two

“unlock” write cycles. These are followed by the program set-up command and data write cycles. Addresses are

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