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AT49F001 Datasheet(PDF) 4 Page - ATMEL Corporation |
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AT49F001 Datasheet(HTML) 4 Page - ATMEL Corporation |
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4 / 16 page  AT49F001(N)(T) 4 ra nge of the bo ot blo ck is 1C000 to 1FFFF fo r th e AT49F001(N)T. Once the feature is enabled, the data in the boot block can no longer be erased or programmed with input voltage lev- els 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 com- mands 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 soft- ware 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 AT49F001(N) and a read from address 1C002H will show if programming the boot block is locked out for the AT49F001(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 identi- fication exit code should be used to return to standard operation. BOOT BLOCK PROGRAMMING LOCKOUT OVERRIDE: The user can override the boot block programming lockout by taking the RESET pin to 12 volts. By doing this, pro- tected boot block data can be altered through a chip erase, sector erase or word programming. When the RESET pin is brought back to TTL levels the boot block programming lockout feature is again active. This feature is not available on the AT49F001N(T). PRODUCT IDENTIFICATION: The product identification mode identifies the device and manufacturer as Atmel. It may be accessed by hardware or software operation. The hardware operation mode can be used by an external pro- grammer 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 AT49F001(N)(T) features DATA polling to indicate the end of a program cycle. During a pro- gram cycle an attempted read of the last byte loaded will result in the complement 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. TOG G LE B I T : I n add ition to D A T A p o lling the AT49F001(N)(T) provides another method for determining 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 tog- gling and valid data will be read. Examining the toggle bit may begin at any time during a program cycle. HARDWARE DATA PROTECTION: Hardware features pr ot ect ag ainst ina d ver t e n t pr og r a ms t o the AT49F001(N)(T) in the following ways: (a) V CC sense: if V CC is below 3.8V (typical), the program function is inhib- ited. (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. |
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Similar Description - AT49F001 |
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