Rainbow Electronics AT49F001NT - Manual (Page 4)

AT49F001(N)(T)
4
ra nge of the bo ot blo ck is 1C000 to 1FFFF fo r th e
AT49F001(N)T.
Once the feature is enabled, the data in the boot block can
no longer be erased or programmed with input voltage lev-
els 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 com-
mands 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 AT49F001(N) and a read from address
1C002H will show if programming the boot block is locked
out for the AT49F001(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 identi-
fication 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. By doing this, pro-
tected boot block data can be altered through a chip erase,
sector erase or word programming. 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 AT49F001N(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 AT49F001(N)(T) features DATA
polling to indicate the end of a program cycle. During a pro-
gram 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
AT49F001(N)(T) 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 tog-
gling 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
AT49F001(N)(T) in the following ways: (a) V
CC
sense: if
V
CC
is below 3.8V (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.