AT49F516 Просмотр технического описания (PDF) - Atmel Corporation
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AT49F516 Datasheet PDF : 13 Pages
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AT49F516
device is updated. This feature does not have to be acti-
vated; the boot block’s usage as a write protected region is
optional to the user. The address range of the boot block is
0000H to 1FFFH.
Once the feature is enabled, the data in the boot block can
no longer be erased or programmed. Data in the main
memory block can still be changed through the regular pro-
gramming method and can be erased using either the chip
erase or the main memory block erase command. 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 0002H 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.
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 AT49F516 features DATA polling to
indicate the end of a program or erase 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.
TOGGLE BIT: In addition to DATA polling the AT49F516
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.
HARDWARE DATA PROTECTION: Hardware features
protect against inadvertent programs to the AT49F516 in
the following ways: (a) VCC sense: if VCC is below 3.8V (typ-
ical), 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.
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