5

AT49BV/LV4096A

1618H–FLASH–4/04

cannot be programmed. The software product identification exit 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 word programming operation. When the RESET pin is

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

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 12. The manufacturer and device codes are the same for

both modes.

DATA POLLING: The AT49BV/LV4096A features Data Polling to indicate the end of a

program 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. During a chip

or sector erase operation, an attempt to read the device will give a “0” on I/O7. Once the

program or erase cycle has completed, true data will be read from the device. Data Poll-

ing may begin at any time during the program cycle.

TOGGLE BIT: In addition to Data Polling, the AT49BV/LV4096A 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 pro-

before programming. (c) Program inhibit: holding any one of OE low, CE high or WE

high inhibits program cycles. (d) Noise filter: pulses of less than 15 ns (typical) on the

WE or CE inputs will not initiate a program cycle.

INPUT LEVELS: While operating with a 2.7V to 3.6V power supply, the address and

control inputs (OE, CE and WE) may be driven from 0 to 5.5V without adversely affect-