Rainbow Electronics AT29BV040A - Manual (Page 2)

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AT29BV040A
0383F–FLASH–05/02
endurance is such that any sector can be written to in excess of 10,000 times. The pro-
gramming algorithm is compatible with other devices in Atmel’s 2.7-volt-only Flash
memories.
To allow for simple in-system reprogrammability, the AT29BV040A does not require
high input voltages for programming. The device can be operated with a single 2.7V to
3.6V supply. Reading data out of the device is similar to reading from an EPROM.
Reprogramming the AT29BV040A is performed on a sector basis; 256 bytes of data are
loaded into the device and then simultaneously programmed.
During a reprogram cycle, the address locations and 256 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 AT29BV040A 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 AT29BV040 has 2048 indi-
vidual sectors, each 256 bytes. Using the software data protection feature, byte loads
are used to enter the 256 bytes of a sector to be programmed. The AT29BV040A 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 256-byte sector must be loaded into the device. The
AT29BV040A automatically 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. The same three program commands must
begin each program operation. All software program commands must obey the sector
program timing specifications. Power transitions will not reset the software data protec-
tion feature, however the software feature will guard against inadvertent program cycles
during power transitions.