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AT49F008 Datasheet(PDF) 3 Page - ATMEL Corporation

Part No. AT49F008
Description  8-Megabit 1M x 8 5-volt Only Flash Memory
Download  12 Pages
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Manufacturer  ATMEL [ATMEL Corporation]
Direct Link  http://www.atmel.com
Logo ATMEL - ATMEL Corporation

AT49F008 Datasheet(HTML) 3 Page - ATMEL Corporation

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AT49F008
3
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 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. If the data on I/O0 is low, the boot block can be
programmed; if the data on I/O0 is high, the program lock-
out feature has been activated and the block 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 12V
± 0.5V. By doing this, pro-
tected 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 AT49F008 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 pro-
gram 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 AT49F008
provides another method for determining the end of a pro-
gram 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
allows for OR - tying of several devices to the same
RDY/BUSY line.
RESET: A RESET input pin is provided to ease some sys-
tem 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, puts the
outputs of the device in a high impedance state, and
reduces the current drawn by the part to a minimum. If the
RESET pin makes a high to low transition during a program
or erase operation, the operation may not be successfully
completed and the operation will have to be repeated 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 feature has been enabled
(see Boot Block Programming Lockout Override section).
HARDWARE DATA PROTECTION: Hardware features
protect against inadvertent programs to the AT49F008 in
the following ways: (a) VCC sense: if VCC is below 3.8V
(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 pro-
gram cycle.


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