4

AT49F001A(N)(T)

3365C–FLASH–9/03

SECTOR ERASE: As an alternative to a full chip erase, the device is organized into sectors

that can be individually erased. There are two 8K-byte parameter block sections and two main

memory blocks. The 8K-byte parameter block sections and the two main memory blocks can

be independently erased and reprogrammed. The Sector Erase command is a six bus cycle

operation. The sector address is latched on the falling 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 operation is internally controlled; it will auto-

matically 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

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 AT49F001A(N) while the address range of the boot block is 1C000 to 1FFFF

for the AT49F001A(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

AT49F001A(N), and a read from address location 1C002H will show if programming the boot

block is locked out for the AT49F001A(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 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.