3

AT49BV/LV1024A

3332B–FLASH–12/03

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 0000H to 1FFFH.

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

grammed. Data in the main memory block can still be changed through the regular

programming method and can be erased using either the Chip Erase or the Main Mem-

ory Block Erase command. 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

programming 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 0002H will show if programming the boot block is locked

out. 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 pro-

grammed. The software product identification exit code should be used to return to

standard operation.

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” (for hardware operation) or “Software Product Identi-

fication Entry/Exit” on page 11. The manufacturer and device code is the same for both

modes.

DATA POLLING: The AT49BV/LV1024A features Data Polling to indicate the end of a

program or erase cycle. During a program cycle an attempted read of the last byte

loaded will result in the complement of the loaded data on I/O7. Once the program cycle

has been completed, true data is valid on all outputs and the next cycle may begin. Data

Polling may begin at any time during the program cycle.

TOGGLE BIT: In addition to Data Polling, the AT49BV/LV1024A provides another

method for determining the end of a program or erase cycle. During a program or erase

operation, successive attempts to read data from the device will result in I/O6 toggling

between one and zero. Once the program cycle has completed, I/O6 will stop toggling

and valid data will be read. Examining the toggle bit may begin at any time during a pro-

gram cycle.

HARDWARE DATA PROTECTION: Hardware features protect against inadvertent

1.8V (typical), the program function is inhibited. (b) Program inhibit: holding any one of

OE low, CE high or WE high inhibits program cycles. (c) Noise filter: pulses of less than

15 ns (typical) on the WE or CE inputs will not initiate a program cycle.