4
AT49F001(N(T)
1008D–FLASH–2/03
SECTOR ERASE: As an alternative to a full chip erase, the device is organized into sectors
that can be individually erased. There are two 8-Kbyte parameter block sections and two main
memory blocks. The 8-Kbyte parameter block sections can be independently erased and
reprogrammed. The two main memory sections are designed to be used as alternative mem-
ory sectors. That is, whenever one of the blocks has been erased and reprogrammed, the
other block should be erased and reprogrammed before the first block is again erased. The
Sector Erase command is a six bus cycle operation. The sector address is latched on the fall-
ing WE
edge of the sixth cycle while the 30H data input command is latched at the rising edge
of WE
. The sector erase starts after the rising edge of WE of the sixth cycle. The erase opera-
tion is internally controlled; it will automatically time to completion.
BYTE PROGRAMMING: Once the memory array is erased, the device is programmed (to a
logical “0”) on a byte-by-byte basis. Please note that a data “0” cannot be programmed back to
a “1”; only erase operations can convert “0”s to “1”s. Programming is accomplished via the
internal device command register and is a 4 bus cycle operation (please refer to the Command
Definitions table). The device will automatically generate the required internal program pulses.
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. Program-
ming is completed after the specified t
BP
cycle time. The DATA polling feature may also be
used to indicate the end of a program cycle.
BOOT BLOCK PROGRAMMING LOCKOUT: The device has one designated block that has
a programming lockout feature. This feature prevents 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 AT49F001(N) while the address range of the boot block is 1C000 to 1FFFF
for the AT49F001(N)T.
Once the feature is enabled, the data in the boot block can no longer be erased or pro-
grammed with input voltage levels 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 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 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 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 pro-
grammed; if the data on I/O0 is high, the program lockout feature has been activated and the
block cannot be programmed. The software product identification exit code should be used to
return to standard operation.
