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Calibration Firmware Features |
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- Calibration Procedure is compatible with the AVR SPI Programming Interface
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Calibration Procedure is compatible with the AVR JTAG Programming Interface
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Algorithm finds the best-fit 'Calibration value' by checking all OSCAL values until the optimum value is found
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Selects best-fit OSCAL value even if there are overlapping OSCAL frequency ranges
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Starts at the lowest frequency first and then works upwards so the AVR device is always kept within its 'Frequency Specification'
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Possibly slower than Atmel AVR055 algorithm but calibration accuracy is usually better
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Accuracy of Oscillator Calibration is usually within +/- 1%
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Programmer uses accurate 32.768 kHz oscillator for the Calibration Procedure
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Best-fit OSCAL value is stored in a specified address in the AVR EEPROM
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Diagnostics including the '% accuracy' and 'number of iterations to reach the optimum OSCAL value' can also be stored in the EEPROM
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Calibration using the SPI Interface |
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- Accurate 32.768 kHz signal is output from the SPI MOSI pin under programmer control during the Calibration Procedure.
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The PASS / FAIL result of the Calibration Firmware is indicated by the AVR Microcontroller asserting the MISO pin back to the programmer.
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The AVR RESET pin must be used in SPI mode to start the Calibration Procedure.
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The SPI Interface can be used for SPI In-System Programming when not being used for the Calibration Procedure.
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Calibration using the JTAG Interface |
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- Accurate 32.768 kHz signal is output from the JTAG TDI pin under programmer control during the Calibration Procedure.
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The PASS / FAIL result of the Calibration Firmware is indicated by the AVR Microcontroller asserting the TDO pin back to the programmer.
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The AVR RESET pin must be used in JTAG mode to start the Calibration Procedure.
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If control of the RESET pin by the programmer in JTAG mode is not possible then a custom version of the 'Calibration Firmware' is required.
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The JTAG Interface can be used for JTAG In-System Programming when not being used for the Calibration Procedure.
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