Rainbow Electronics AT49LV001NT - Manual (Page 4)

AT49BV/LV001(N)(T)
4
Once the feature is enabled, the data in the boot block can
no longer be erased or programmed with input voltage level
of 5.5V or less. Data in the main memory block can still be
changed through the regular programming method. To acti-
vate 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 soft-
ware 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 AT49BV/LV001(N) and a read from
address 1C002H will show if programming the boot block is
locked out for the AT49BV/LV001(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 acti-
vated and the block cannot be programmed. The software
product identification code should be used to return to stan-
dard 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 levels the boot block
programming lockout feature is again active. This feature is
not available on the AT49BV/LV001N(T).
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/LV001(N)(T) 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.
T O G G L E B I T : I n a d d i t i o n t o D A T A p o l l i n g t h e
AT49BV/LV001(N)(T) provides another method for deter-
mining the end of a program or erase cycle. During a pro-
gram 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.
HARDWARE DATA PROTECTION: Hardware features
p r o t e c t a g a i n s t i n a d v e r t e n t p r o g r a m s t o t h e
AT49BV/LV001(N)(T) in the following ways: (a) V
CC
sense:
if V
CC
is below 1.8V (typical), the program function is inhib-
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.