AT29C1024-12 ATMEL Corporation, AT29C1024-12 Datasheet - Page 2

• Manufacturer Part Number: AT29C1024-12
• Description: 1 Megabit 64K x 16 5-volt Only CMOS Flash Memory
• Manufacturer: ATMEL Corporation

Description (Continued)
To allow for simple in-system reprogrammability, the
AT29C1024 does not require high input voltages for pro-
gramming. Five-volt-only commands determine the opera-
tion of the device. Reading data out of the device is similar
to reading from an EPROM. Reprogramming the
AT29C1024 is performed on a sector basis; 128 words of
data are loaded into the device and then simultaneously
programmed.
Block Diagram
Device Operation
READ:
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.
DATA LOAD:
words of a sector to be programmed or the software codes
for data protection. A data load is performed by applying a
low pulse on the WE or CE input with CE or WE low (re-
spectively) 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.
PROGRAM:
basis. If a word of data within a sector is to be changed,
data for the entire sector must be loaded into the device.
Any word that is not loaded during the programming of its
sector will be erased to read FFH. 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 s 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 s 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
4-142
The AT29C1024 is accessed like an EPROM.
The device is reprogrammed on a sector
Data loads are used to enter the 128
AT29C1024
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
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.
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-
ration of t
operation.
SOFTWARE DATA PROTECTION:
led data protection feature is available on the AT29C1024.
Once the software protection is enabled a software algo-
rithm must be issued to the device before a program may
be performed. The software protection feature may be en-
abled or disabled by the user; when shipped from Atmel,
the software data protection feature is disabled. To enable
the software data protection, a series of three program
commands to specific addresses with specific data must
be performed. After the software data protection is en-
abled the same three program commands must begin
each program cycle in order for the programs to occur. All
software program commands must obey the sector pro-
gram timing specifications. Once set, software data pro-
tection will remain active unless the disable command se-
quence is issued. Power transitions will not reset the soft-
ware data protection feature, however the software fea-
ture will guard against inadvertent program cycles during
power transitions.
WC
, a read operation will effectively be a polling
A software control-
(continued)