AT49BV040A Просмотр технического описания (PDF) - Atmel Corporation
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AT49BV040A Datasheet PDF : 17 Pages
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of the device is updated. This feature does not have to be activated; the boot block’s usage as
a write protected region is optional to the user. The address range of the boot block is 00000
to 03FFF.
Once the feature is enabled, the data in the boot block can no longer be erased or pro-
grammed. 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 commands to
specific addresses with specific data must be performed. Please refer to the Command Defini-
tions table.
BOOT BLOCK LOCKOUT DETECTION: A software method is available to determine if pro-
gramming of the boot block section is locked out. When the device is in the software 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 lockout
feature has been activated and the block cannot be programmed. The software product identi-
fication code should be used to return to standard operation.
PRODUCT IDENTIFICATION: The product identification mode identifies the device and man-
ufacturer 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 Identification.
The manufacturer and device code is the same for both modes.
DATA POLLING: The AT49BV040A 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 com-
plement 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 addition to DATA polling the AT49BV040A provides another method for
determining the end of a program or erase cycle. During a program or erase operation, suc-
cessive 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 protect against inadvertent programs
to the AT49BV040A in the following ways: (a) VCC sense: if VCC is below 1.8V (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 program cycle.
4 AT49BV040A
3358A–FLASH–6/03
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