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2467S–AVR–07/09
ATmega128
the EESAVE fuse which will take effect once it is programmed. The fuses are also latched on
power-up in normal mode.
Signature Bytes All Atmel microcontrollers have a three-byte signature code which identifies the device. This
code can be read in both serial and parallel mode, also when the device is locked. The three
bytes reside in a separate address space.
For the ATmega128 the signature bytes are:
1. $000: $1E (indicates manufactured by Atmel)
2. $001: $97 (indicates 128KB Flash memory)
3. $002: $02 (indicates ATmega128 device when $001 is $97)
Calibration Byte The ATmega128 stores four different calibration values for the internal RC Oscillator. These
bytes resides in the signature row high byte of the addresses 0x000, 0x0001, 0x0002, and
0x0003 for 1, 2, 4, and 8 MHz respectively. During Reset, the 1 MHz value is automatically
loaded into the OSCCAL Register. If other frequencies are used, the calibration value has to be
loaded manually, see “Oscillator Calibration Register – OSCCAL” on page 42 for details.
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