MBM29LV400TC-70/-90/-12/MBM29LV400BC-70/-90/-12
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
command register is written by bringing WE to VIL, while CE is at VIL and OE is at VIH. Addresses are latched on
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 Protection
The MBM29LV400TC/BC feature hardware sector protection. This feature will disable both program and erase
operations in any number of sectors (0 through 10). The sector protection feature is enabled using programming
equipment at the user’s site. The devices are shipped with all sectors unprotected. Alternatively, Fujitsu may
program and protect sectors in the factory prior to shiping the device.
To activate this mode, the programming equipment must force VID on address pin A9 and control pin OE, (suggest
VID = 11.5 V), CE = VIL, and A6 = VIL. The sector addresses ( A17, A16, A15, A14, A13, and A12) should be set to the
sector to be protected. Tables 5 and 6 define the sector address for each of the eleven (11) individual 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 Figures 16 and 24
for sector protection waveforms and algorithm.
To verify programming of the protection circuitry, the programming equipment must force VID on address pin A9
with CE and OE at VIL and WE at VIH. Scanning the sector addresses ( A17, A16, A15, A14, A13, and A12) while (A6,
A1, A0) = (0, 1, 0) will produce a logical “1” code at device output DQ0 for a protected sector. Otherwise the
devices will read 00H for unprotected sector. In this mode, the lower order addresses, except for A0, A1, and A6
are DON’T CARES. Address locations with A1 = VIL are reserved for Autoselect manufacturer and device codes.
A-1 requires to apply to VIL on byte mode.
ItisalsopossibletodetermineifasectorisprotectedinthesystembywritinganAutoselectcommand. Performing
a read operation at the address location XX02H, where the higher order addresses (A17, A16, A15, A14, A13, and
A12) are the desired sector address will produce a logical “1” at DQ0 for a protected sector. See Tables 4.1 and
4.2 for Autoselect codes.
Temporary Sector Unprotection
This feature allows temporary unprotection of previously protected sectors of the MBM29LV400TC/BC 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 RESETpin, all the previously protected sectors will be protected
again. See Figures 17 and 25.
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FUJITSU [ FUJITSU ]
