4

AT49BV/LV4096A

1618H–FLASH–4/04

CHIP ERASE: The entire device can be erased at one time by using the 6-byte chip

erase software code. After the chip erase has been initiated, the device will internally

time the erase operation so that no external clocks are required. The maximum time to

erase the chip is t

If the boot block lockout has been enabled, the chip erase will not erase the data in the

boot block; it will erase the main memory block and the parameter blocks only. After the

chip erase, the device will return to the read or standby mode.

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

sectors that can be individually erased. There are two 4K word parameter block sec-

tions, one boot block, and the main memory array block. 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 automatically time to completion. Whenever the main memory

block is erased and reprogrammed, the two parameter blocks should be erased and

reprogrammed before the main memory block is erased again. Whenever a parameter

block is erased and reprogrammed, the other parameter block should be erased and

reprogrammed before the first parameter block is erased again. Whenever the boot

block is erased and reprogrammed, the main memory block and the parameter blocks

should be erased and reprogrammed before the boot block is erased again.

BYTE/WORD PROGRAMMING: Once a memory block is erased, it is programmed (to

a logic “0”) on a byte-by-byte or word-by-word basis. Programming is accomplished via

the internal device command register and is a four-bus cycle operation. The device will

automatically generate the required internal program pulses.

Any commands written to the chip during the embedded programming cycle will be

ignored. If a hardware reset happens during programming, the data at the location being

programmed will be corrupted. 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 completed after

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 8K

words. 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 00000H to 01FFFH.

Once the feature is enabled, the data in the boot block can no longer be erased or pro-

grammed when input levels of 5.5V or less are used. 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

programming 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 the following address location will show if programming the boot block is

locked out – 00002H. 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 enabled and the block