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AT49F040B Datasheet(PDF) 4 Page - ATMEL Corporation

Part No. AT49F040B
Description  4-megabit (512K x 8) 5-volt Only Flash Memory
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Maker  ATMEL [ATMEL Corporation]
Homepage  http://www.atmel.com
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AT49F040B Datasheet(HTML) 4 Page - ATMEL Corporation

 
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4
3606A–FLASH–12/05
AT49F040B
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 t
BP 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.
4.5.1
Boot Sector Lockout Detection
A software method is available to determine if programming of the boot sector is locked out.
When the device is in the software product identification mode (see Software Product Identification
Entry/Exit on page 15
) a read from address location 00002H will show if programming the boot
sector is locked out. If the data on I/O0 is low, the boot sector can be programmed; if the data on
I/O0 is high, the program lockout feature has been activated and the sector cannot be pro-
grammed. The software product identification code should be used to return to standard
operation.


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