AT49BV002A-70VI Ver la hoja de datos (PDF) - Atmel Corporation

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AT49BV002A-70VI

2-megabit(256K x 8) Single 2.7-volt Battery-Voltage Flash Memory

Atmel Corporation 

AT49BV002A(N)(T)

The program cycle has addresses latched on the falling edge of WE or CE, whichever occurs

last, and the data latched on the rising edge of WE or CE, whichever occurs first. Programming

is completed after the specified tBP cycle time. The DATA polling feature may also be used to

indicate the end of a program cycle.

4.6 Boot Block Programming Lockout

The device has one designated block that has a programming lockout feature. This feature pre-

vents programming of data in the designated block once the feature has been enabled. The size

of the block is 16K bytes. This block, referred to as the boot block, can contain secure code that

is used to bring up the system. Enabling the lockout feature will allow the boot code to stay in the

device while data in the rest of the device is updated. This feature does not have to be activated;

the boot block’s usage as a write protected region is optional to the user. The address range of

the boot block is 00000 to 03FFF for the AT49BV002A(N) while the address range of the boot

block is 3C000 to 3FFFF for the AT49BV002A(N)T.

Once the feature is enabled, the data in the boot block can no longer be erased or programmed

with input voltage of 5.5V or less. Data in the main memory block can still be changed through

the regular programming method. To activate the lockout feature, a series of six program com-

mands to specific addresses with specific data must be performed. Please refer to the

“Command Definition Table” on page 7.

4.6.1

Boot Block Lockout Detection

A software method is available to determine if programming of the boot block section is locked

out. When the device is in the software product identification mode (see “Software Product Iden-

tification Entry and Exit” sections) a read from address location 00002H will show if

programming the boot block is locked out for the AT49BV002A(N), and a read from address

location 3C002H will show if programming the bootblock is locked out for AT49BV002A(N)T. If

the data on I/O0 is low, the boot block can be programmed; if the data on I/O0 is high, the pro-

gram lockout feature has been activated and the block cannot be programmed. The software

product identification code should be used to return to standard operation.

4.6.2

Boot Block Programming Lockout Override

The user can override the boot block programming lockout by taking the RESET pin to 12 volts

during the entire chip erase, sector erase or byte programming operation. When the RESET pin

is brought back to TTL levels the boot block programming lockout feature is again active. This

feature is not available on the AT49BV002AN(T).

4.7 Product Identification

The product identification mode identifies the device and manufacturer as Atmel. It may be

accessed by hardware or software operation. The hardware operation mode can be used by an

external programmer to identify the correct programming algorithm for the Atmel product.

For details, see “Operating Modes” on page 8 (for hardware operation) or Software Product

Identification. The manufacturer and device code is the same for both modes.

5

3353G–FLASH–8/05

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