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 Prod-

uct Identification Entry and Exit sections) a read from ad-

dress location 00002H 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 programmed. The software product identifica-

tion exit code should be used to return to standard opera-

tion.

BOOT BLOCK PROGRAMMING LOCKOUT OVER-

RIDE: The user can override the boot block programming

lockout by taking the RESET pin to 12 + 0.5 volts. By doing

this, protected boot block data can be altered through a

chip erase, or byte programming. 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 pro-

grammer 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.

DATA POLLING: The AT49BV/LV080 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. DATA

polling may begin at any time during the program cycle.

TOGGLE BIT: In ad di ti on t o DATA po ll in g, t h e

AT49BV/LV080 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 program cycle.

RDY/BUSY: An open drain READY/BUSY output pin pro-

vides another method of detecting the end of a program or

erase operation. RDY/BUSY is actively pulled low during

the internal program and erase cycles and is released at

the completion of the cycle. The open drain connection al-

lows for OR - tying of several devices to the same

RDY/BUSY line.

RESET: A RESET input pin is provided to ease some

system applications. When RESET is at a logic high level,

the device is in its standard operating mode. A low level on

the RESET input halts the present device operation and

puts the outputs of the device in a high impedance state.

If the RESET pin makes a high to low transition during a

program or erase operation, the operation may not be suc-

cessfully completed, and the operation will have to be re-

peated after a high level is applied to the RESET pin.

When a high level is reasserted on the RESET pin, the

device returns to the read or standby mode, depending

upon the state of the control inputs. By applying a 12V +

0.5V input signal to the RESET pin the boot block array

can be reprogrammed even if the boot block lockout fea-

ture has been enabled (see Boot Block Programming

Lockout Override section).

HARDWARE DATA PROTECTION: Hardware features

pr otect ag ai nst i n a d ve r t e n t p r og r a m s t o th e

ited. (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.

Device Operation (Continued)

AT49BV/LV080

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