Rainbow Electronics AT29LV512 - Manual (Page 2)

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AT29LV512
0177M–05/02
To allow for simple in-system reprogrammability, the AT29LV512 does not require high
input voltages for programming. Three-volt-only commands determine the operation of
the device. Reading data out of the device is similar to reading from an EPROM. Repro-
gramming the AT29LV512 is performed on a sector basis; 128 bytes of data are loaded
into the device and then simultaneously programmed.
During a reprogram cycle, the address locations and 128 bytes of data are captured at
microprocessor speed and internally latched, freeing the address and data bus for other
operations. Following the initiation of a program cycle, the device will automatically
erase the sector and then program the latched data using an internal control timer. The
end of a program cycle can be detected by DATA polling of I/O7. Once the end of a pro-
gram cycle has been detected, a new access for a read or program can begin.
Block Diagram
Device Operation
READ: The AT29LV512 is accessed like an EPROM. When CE and OE are low and
WE is high, the data stored at the memory location determined by the address pins
is asserted on the outputs. The outputs are put in the high impedance state whenever
CE or OE is high. This dual-line control gives designers flexibility in preventing bus
contention.
SOFTWARE DATA PROTECTION PROGRAMMING: The AT29LV512 has 512 individ-
ual sectors, each 128 bytes. Using the software data protection feature, byte loads are
used to enter the 128 bytes of a sector to be programmed. The AT29LV512 can only be
programmed or reprogrammed using the software data protection feature. The device is
programmed on a sector basis. If a byte of data within the sector is to be changed, data
for the entire 128-byte sector must be loaded into the device. The AT29LV512 automat-
ically does a sector erase prior to loading the data into the sector. An erase command is
not required.
Software data protection protects the device from inadvertent programming. A series of
three program commands to specific addresses with specific data must be presented to
the device before programming may occur. After writing the three-byte command
sequence (and after t
WC
), the entire device is protected. The same three program com-
mands must begin each program operation. All software program commands must obey
the sector program timing specifications. Power transitions will not reset the software
data protection feature; however, the software feature will guard against inadvertent
program cycles during power transitions.