Atmel AVR ISP, User Manual

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Software Front-end
4-6 AVR
®
In System Programmer User Guide
4.3.4 “Advanced”
Settings The Advanced tab is currently divided into two sub groups.
Figure 4-5. Advanced Settings
4.3.4.1 Signature Bytes By pressing the “Read Signature” button, the signature bytes are read from the target
device. The signature bytes act like an identifier for the part. Please refer to the AVR
datasheets for more information about signature bytes.
4.3.4.2 Oscillator
Calibration Byte For devices with calibratable Internal RC Oscillator, the oscillator calibration byte is writ-
ten to the device during manufacturing, and cannot be erased or altered by the user.
The calibration byte is a tuning value that should be written to the OSCCAL register in
order to tune the internal RC to specified frequency.
4.3.4.3 Reading Oscillator
Calibration Byte By pressing the “Read Cal. Byte” button, the calibration value is read from the device
and shown in the “Value” text box. If this option is grayed out, the selected device does
not have a tunable internal RC Oscillator. On selected devices, the RC oscillator is self-
calibrating. On these devices there is no need to handle the Calibration byte manually
(for more information see appropriate device datasheet).
4.3.4.4 Writing Oscillator
Calibration Byte Since the calibration byte is not directly accessible during program execution on devices
without automatic RC calibration, the user should write the calibration byte into a known
location in Flash or EEPROM memory. Do this by writing the desired memory address in
the “Write Address” text box and then press the “Write to Memory” button. The calibra-
tion byte is then written to the memory indicated by the “Flash” and “EEPROM” radio
buttons.
4.3.5 “Board” Settings The Board tab allows changing the operating conditions for the AVRISP programmer.
The AVRISP allows modification of the Oscillator frequency.