at49bv002an ATMEL Corporation, at49bv002an Datasheet - Page 5

• Manufacturer Part Number: at49bv002an
• Description: 2-megabit 256k X 8 Single 2.7-volt Battery-voltage Flash Memory
• Manufacturer: ATMEL Corporation

4.6
4.6.1
4.6.2
4.7
3353G–FLASH–8/05
Boot Block Programming Lockout
Product Identification
Boot Block Lockout Detection
Boot Block Programming Lockout Override
The program cycle has addresses latched on the falling edge of WE or CE, whichever occurs
last, and the data latched on the rising edge of WE or CE, whichever occurs first. Programming
is completed after the specified t
indicate the end of a program cycle.
The device has one designated block that has a programming lockout feature. This feature pre-
vents programming of data in the designated block once the feature has been enabled. The size
of the block is 16K bytes. This block, referred to as the boot block, can contain secure code that
is used to bring up the system. Enabling the lockout feature will allow the boot code to stay in the
device while data in the rest 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 for the AT49BV002A(N) while the address range of the boot
block is 3C000 to 3FFFF for the AT49BV002A(N)T.
Once the feature is enabled, the data in the boot block can no longer be erased or programmed
with input voltage 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 Definition Table” on page
A software method is available to determine if programming of the boot block section is locked
out. When the device is in the software product identification mode (see
tification Entry and Exit”
programming the boot block is locked out for the AT49BV002A(N), and a read from address
location 3C002H will show if programming the bootblock is locked out for AT49BV002A(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 pro-
gram lockout feature has been activated and the block cannot be programmed. The software
product identification code should be used to return to standard operation.
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 AT49BV002AN(T).
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 programmer to identify the correct programming algorithm for the Atmel product.
For details, see
Identification. The manufacturer and device code is the same for both modes.
“Operating Modes” on page 8
sections) a read from address location 00002H will show if
BP
cycle time. The DATA polling feature may also be used to
7.
(for hardware operation) or Software Product
AT49BV002A(N)(T)
“Software Product Iden-
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