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MBM29LV008BA

FLASH MEMORY CMOS 8M (1M × 8) BIT

Spansion Inc. 

MBM29LV008TA/BA-70/90

Temporary Sector Unprotection

This feature allows temporary unprotection of previously protected sectors of the MBM29LV008TA/BA devices

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

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

addresses. Once the 12 V is taken away from the RESET pin, all the previously protected sectors will be protected

again. See “ (11) Temporary Sector Unprotection Timing Diagram” in s TIMING DIAGRAM and “ (6) Temporary

Sector 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 devices to the

read mode. “MBM29LV008TA/008BA Standard Command Definitions” in s DEVICE BUS OPERATION 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

In order to return from Autoselect mode or Exceeded Timing Limits (DQ5 = 1) to read/reset mode, the read/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 devices remain enabled for reads until the command

register contents are altered.

The devices 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 devices reside in the target system. PROM

programmers typically access the signature codes by raising A9 to a high voltage. However, multiplexing high

voltage onto the address lines is not generally desired 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 (MBM29LV008TA = 3Eh and MBM29LV008BA = 37h). (See

“MBM29LV008TA/008BA Sector Protection Verify Autoselect Codes” and “Expanded Autoselect Code Table”

in s DEVICE BUS OPERATION.) All manufacturer and device codes will exhibit odd parity with DQ7 defined as

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

Scanning the sector addresses (A19, A18, A17, A16, A15, A14, and A13) while (A10, A6, A1, A0) = (0, 0, 1, 0) will produce

a logical “1” at device output DQ0 for a protected sector. The programming verification should be perform margin

mode on the protected sector. (See “MBM29LV008TA/008BA Sector Protection Verify Autoselect Codes” and

“Expanded Autoselect Code Table” in s DEVICE BUS OPERATION.)

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.

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