Datasheet

Clock Sources

ATmega8A Boot Loader Parameters

Calibrated Internal RC Oscillator

Low-frequency Crystal Oscillator

29.2.1 Latching of Fuses

The fuse values are latched when the device enters programming mode and changes of the fuse values

will have no effect until the part leaves Programming mode. This does not apply to the EESAVE Fuse

which will take effect once it is programmed. The fuses are also latched on Power-up in Normal mode.

29.3 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 ATmega8A the signature bytes are given in the following table.

Table 29-5. Device ID

Part Signature Bytes Address

0x000 0x001 0x002

ATmega8A 0x1E 0x93 0x07

29.4 Calibration Byte

The ATmega8A stores four different calibration values for the internal RC Oscillator. These bytes resides

in the signature row High byte of the addresses 0x0000, 0x0001, 0x0002, and 0x0003 for 1, 2, 4, and

8MHz respectively. During Reset, the 1MHz value is automatically loaded into the OSCCAL Register. If

other frequencies are used, the calibration value has to be loaded manually, see OSCCAL – Oscillator

Calibration Register for details.