AT29LV512_ 查看數據表（PDF） - Atmel Corporation

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AT29LV512_

512K (64K x 8) 3-volt Only CMOS Flash Memory

Atmel Corporation 

Description (Continued)

To allow for simple in-system reprogrammability, the

AT29LV512 does not require high input voltages for pro-

gramming. Three-volt-only commands determine the op-

eration of the device. Reading data out of the device is

similar to reading from an EPROM. Reprogramming the

AT29LV512 is performed on a sector basis; 128-bytes of

data are loaded into the device and then simultaneously

programmed.

Block Diagram

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 cy-

cle, 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 poll-

ing of I/O7. Once the end of a program cycle has been

detected, a new access for a read or program can begin.

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 individual 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 fea-

ture. The device is programmed on a sector basis. If a byte

of data within the sector is to be changed, data for the en-

tire 128-byte sector must be loaded into the device. The

AT29LV512 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. After writing

the three-byte command sequence (and after tWC), the en-

tire device is protected. The same three program com-

mands must begin each program operation. All software

4-44

AT29LV512

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.

Any attempt to write to the device without the 3-byte 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-byte command code

is given, a byte 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-bytes of data must be loaded into each sector.

Any byte that is not loaded during the programming of its

sector will be erased to read FFh. Once the bytes of a sec-

tor are loaded into the device, they are simultaneously

programmed during the internal programming period. Af-

ter the first data byte has been loaded into the device, suc-

cessive bytes are entered in the same manner. Each new

byte 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 byte. If a high to low transition

is not detected within 150 µs of the last low to high transi-

tion, the load period will end and the internal programming

(continued)

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