Datasheet

13.11 System Clock Prescaler

32.2.1 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.

32.3 Signature Bytes

The device have a three-byte signature code. 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 device, the

signature bytes are given in the following table.

Table 32-9. Device ID

Part Signature Bytes Address

0x000 0x001 0x002

ATmega48PA 0x1E 0x92 0x0A

ATmega88PA 0x1E 0x93 0x0F

ATmega168PA 0x1E 0x94 0x0B

32.4 Calibration Byte

The device has a byte calibration value for the Internal RC oscillator. This byte resides in the high byte of

address 0x000 in the signature address space. During Reset, this byte is automatically written into the

OSCCAL register to ensure correct frequency of the calibrated RC oscillator.