4

AT49BV001A(N)(T)

3364C–FLASH–9/03

BYTE PROGRAMMING: Once the memory array is erased, the device is programmed (to a

logical “0”) on a byte-by-byte basis. Please note that a data “0” cannot be programmed back to

a “1”; only erase operations can convert “0”s to “1”s. Programming is accomplished via the

internal device command register and is a 4 bus cycle operation (please refer to the Command

Definitions table). The device will automatically generate the required internal program pulses.

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. Program-

ming is completed after the specified t

used to indicate the end of a program cycle.

BOOT BLOCK PROGRAMMING LOCKOUT: The device has one designated block that has

a programming lockout feature. This feature prevents 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 AT49BV001A(N) while the address range of the boot block is 1C000 to

1FFFF for the AT49BV001A(N)T.

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

grammed 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 commands to specific addresses with specific data must be performed. Please

refer to the Command Definitions table.

BOOT BLOCK LOCKOUT DETECTION: A software method is available to determine if pro-

gramming of the boot block section is locked out. When the device is in the software product

identification mode (see Software Product Identification Entry and Exit sections) a read from

address location 00002H will show if programming the boot block is locked out for the

AT49BV001A(N), and a read from address location 1C002H will show if programming the boot

block is locked out for the AT49BV001A(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 program lockout feature has been activated and

the block cannot be programmed. The software product identification code should be used to

return to standard operation.

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 lev-

els the boot block programming lockout feature is again active. This feature is not available on

the AT49BV001AN(T).

PRODUCT IDENTIFICATION: The product identification mode identifies the device and man-

ufacturer 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 (for hardware operation) or Software Product Identification.

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