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AT49F040T Datasheet(PDF) 3 Page - ATMEL Corporation |
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AT49F040T Datasheet(HTML) 3 Page - ATMEL Corporation |
3 / 12 page ![]() AT49F040/040T 3 boot block is 00000H to 03FFFH while the address range of the AT49F040T boot block is 7C000H to 7FFFFH. Once the feature is enabled, the data in the boot block can no longer be erased or programmed. Data in the main memory block can still be changed through the regular pro- gramming method. To activate the lockout feature, a series of six program commands to specific addresses with spe- cific 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. If the data on I/O0 is low, the boot block can be programmed; if the data on I/O0 is high, the program lock- out feature has been activated and the block cannot be programmed. The software product identification code should be used to return to standard operation. 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 AT49F040 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 complement of the loaded data on I/O7. Once the pro- gram 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 AT49F040 provides another method for determining the end of a pro- gram 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. Examining the toggle bit may begin at any time during a program cycle. HARDWARE DATA PROTECTION: Hardware features protect against inadvertent programs to the AT49F040 in the following ways: (a) V CC sense: if VCC is below 3.8V (typ- ical), the program 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. |
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