AT29LV1024 Просмотр технического описания (PDF) - Atmel Corporation
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AT29LV1024 Datasheet PDF : 10 Pages
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Description (Continued)
EPROM. Reprogramming the AT29LV1024 is performed
on a sector basis; 128 words of data are loaded into the
device and then simultaneously programmed.
During a reprogram cycle, the address locations and 128
words of data are internally latched, freeing the address
and data bus for other operations. Following the initiation
of a program cycle, the device will automatically erase the
Block Diagram
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 or I/O15. Once the end of a pro-
gram cycle has been detected, a new access for a read or
program can begin.
Device Operation
READ: The AT29LV1024 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 AT29LV1024 has 512 individual sectors, each 128
words. Using the software data protection feature, word
loads are used to enter the 128 words of a sector to be
programmed. The AT29LV1024 can only be programmed
or reprogrammed using the software data protection fea-
ture. The device is programmed on a sector basis. If a
word of data within the sector is to be changed, data for
the entire 128 word sector must be loaded into the device.
The AT29LV1024 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 inadver-
tent 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 op-
eration. 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 pro-
gram cycles during power transitions.
4-64
AT29LV1024
Any attempt to write to the device without the 3 word com-
mand sequence will start the internal write timers. No data
will be written to the device; however, for the duration of
tWC, a read operation will effectively be a polling operation.
After the software data protection’s 3 word command code
is given, a word load is performed by applying a low pulse
on the WE or CE input with CE or WE low (respectively)
and OE high. The address is latched on the falling edge of
CE or WE, whichever occurs last. The data is latched by
the first rising edge of CE or WE.
The 128 words of data must be loaded into each sector.
Any word that is not loaded during the programming of its
sector will be erased to read FFFFH. Once the words of a
sector are loaded into the device, they are simultaneously
programmed during the internal programming period. Af-
ter the first data word has been loaded into the device,
successive words are entered in the same manner. Each
new word to be programmed must have its high to low
transition on WE (or CE) within 150 µs of the low to high
transition of WE (or CE) of the preceding word. If a high to
low transition is not detected within 150 µs of the last low
to high transition, the load period will end and the internal
programming period will start. A7 to A15 specify the sector
address. The sector address must be valid during each
high to low transition of WE (or CE). A0 to A6 specify the
word address within the sector. The words may be loaded
in any order; sequential loading is not required. Once a
programming operation has been initiated, and for the du-
(continued)
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