AT49F040A(2003) 查看數據表（PDF） - Atmel Corporation

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AT49F040A
(Rev.:2003)

4-megabit (512K x 8) 5-volt Only Flash Memory

Atmel Corporation 

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.

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

grammed. 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 Defini-

tions 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. 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 identi-

fication exit code should be used to return to standard operation.

PRODUCT IDENTIFICATION: The product identification mode identifies the device and man-

ufacturer as Atmel. It may be accessed by hardware or software operation. The hardware

operation mode can be used by an external programmer to identify the correct programming

algorithm for the Atmel product.

For details, see Operating Modes (for hardware operation) or Software Product Identification.

The manufacturer and device code is the same for both modes.

DATA POLLING: The AT49F040A features DATA polling to indicate the end of a program

cycle. During a program cycle an attempted read of the last byte loaded will result in the com-

plement of the loaded data on I/O7. Once the program cycle has been completed, true data is

valid on all outputs and the next cycle may begin. DATA polling may begin at any time during

the program cycle.

TOGGLE BIT: In addition to DATA polling the AT49F040A provides another method for deter-

mining the end of a program or erase cycle. During a program or erase operation, successive

attempts to read data from the device will result in I/O6 toggling between one and zero. Once

the program cycle has completed, I/O6 will stop toggling and valid data will be read. Examin-

ing the toggle bit may begin at any time during a program cycle.

HARDWARE DATA PROTECTION: Hardware features protect against inadvertent programs

to the AT49F040A in the following ways: (a) VCC sense: if VCC is below 3.8V (typical), the pro-

gram function is inhibited. (b) Program inhibit: holding any one of OE low, CE high or WE high

inhibits program cycles. (c) Noise filter: pulses of less than 15 ns (typical) on the WE or CE

inputs will not initiate a program cycle.

4 AT49F040A

3359A–FLASH–6/03

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