AT49BV040B View Datasheet(PDF) - Atmel Corporation

Part Name

Description

Manufacturer

AT49BV040B

4-megabit (512K x 8) Flash Memory

Atmel Corporation 

4.3 Erasure

Before a byte can be reprogrammed, it must be erased. The erased state of memory bits is a

logical “1”. The entire device can be erased by using the Chip Erase command or individual sec-

tors can be erased by using the Sector Erase command.

4.3.1

Chip Erase

If the boot block lockout has been enabled, the Chip Erase function will erase Parameter Sector

1, Parameter Sector 2, Main Memory Sectors 1 - 8, but not the boot sector. If the Boot Sector

Lockout has not been enabled, the Chip Erase function will erase the entire chip. After the full

chip erase the device will return back to read mode. Any command during chip erase will be

ignored.

4.3.2

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 sectors and eight main memory sectors. The 8K-byte

parameter sectors and the eight main memory sectors can be independently erased and repro-

grammed. 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.

4.4 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 (see “Command Definition Table” on page 7). 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. Programming

is completed after the specified tBP cycle time. The DATA polling or toggle bit feature may also

be used to indicate the end of a program cycle.

4.5 Boot Sector Programming Lockout

The device has one designated sector that has a programming lockout feature. This feature pre-

vents programming of data in the designated sector once the feature has been enabled. The

size of the sector is 16K bytes. This sector, referred to as the boot sector, 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 sector’s usage as a write protected region is optional to the user. The

address range of the boot sector is 00000 to 03FFF.

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

grammed. Data in the main memory and parameter sectors 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. See “Command Definition Table” on

page 7.

4 AT49BV040B

3499B–FLASH–4/06

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