Flash Memory - Application Notes - Atmel Corporation

Recommended Reprogramming Procedure for

Atmel’s Flash Memories

The AT49X001(N)(T), AT49X002(N)(T),

AT49X2048A(T), AT49X4096A(T),

AT49X8192A(T) (the X designation

could refer to BV, LV, or F) are sectored

Flash memory devices. The memory

array of each device is divided into multi-

ple sectors, which can be used to store

program code or data. The

AT49X001(N)(T) and the

AT49X002(N)(T) devices are byte-wide

memories that consist of two parameter

blocks, two main memory blocks, and a

boot block. The AT49X2048A(T),

AT49X4096A(T), and AT49X8192A(T)

are byte or word selectable through the

BYTE pin. All three of these memories

consist of two parameter blocks, one

boot block and one main memory block.

All five of these memories can be repro-

grammed by first performing a chip

erase and then programming the mem-

ory byte by byte or word by word. This is

the recommend method of reprogram-

ming the whole device. A sector erase

command is also available on all of

these devices. The sector erase com-

mand only erases a particular region in

the memory. After the region is erased, it

can be programmed with new data.

There are, however, certain restrictions

that must be obeyed when using sector

erases. The restrictions for the

AT49X001(N)(T) and the

AT49X002(N)(T) are slightly different

than the restrictions for the

AT49X2048A(T), AT49X4096A(T), and

the AT49X8192A(T). If the restrictions

are not adhered to, incorrect data could

be stored and later read from the device.

For the AT49X002 (N)(T) and the

AT49X001(N)(T), the two main memory

sectors are designed such that sector

erases of one main memory block must

alternate with sector erases of the other

main memory block. Repeated attempts

to erase and reprogram either Main

Memory Block 1 or Main Memory Block

2 may disturb the data in other memory

blocks. By alternating updates between

Main Memory Blocks 1 and 2, the mem-

ory contents will not be disturbed. It is

critical that whenever a main memory

block is erased and reprogrammed the

other main memory block should be

erased and reprogrammed prior to any

subsequent erase of the first block. Fail-

ure to perform the above mentioned

procedure could result in incorrect data

being read from the device. Each param-

eter block can be updated

independently; erases to the parameter

blocks do not need to be alternated with

any other erases. Please note that there

is no mechanism to erase just the boot

block in these devices.

For the AT49X2048A, AT49X4096A,

and the AT49X8192A, the parameter

blocks are designed such that sector

erases of one parameter block must

alternate with sector erases of the other

parameter block. Repeated attempts to

erase and reprogram Parameter Block 1

or Parameter Block 2 may disturb the

data in the other parameter block. By

alternating updates between Parameter

Blocks 1 and 2, the memory contents will

not be disturbed. It is critical that when-

ever a parameter block is erased and

reprogrammed the other parameter

block should be erased and repro-

grammed prior to any subsequent erase

of the first parameter block. The main

memory region does not need to be

reprogrammed even if the parameter

Recommended

Reprogramming

Procedure for

Atmel’s Flash

Memories

Application

Note

Rev. 1913A–05/00

Flash

blocks receive multiple updates, however, whenever the

main memory block is erased and reprogrammed, the two

parameter blocks should be erased and reprogrammed

before the main memory is erased again. Similarly, the

boot region does not need to be reprogrammed even if the

parameter and main memory sectors receive multiple

updates, but when the boot block region is erased and

reprogrammed, the main memory and the parameter

blocks should be erased and reprogrammed before the

boot block is erased again. Failure to perform the above

mentioned procedure could result in incorrect data being

read from the device.

Note that the possible disturb effect only occurs during an

erase operation not a programming operation (due to the

shortness of the programming cycle). Please contact Atmel

regarding any questions on the erasing or programming of

any one of these five devices.

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