Fuse Bits
The device has three Fuse bytes. The following tables describe briefly the functionality of all the fuses and how they are mapped into the Fuse bytes. Note that the fuses are read as logical zero, '0', if they are programmed.
| Low Fuse Byte | Bit No. | Description | Default Value |
|---|---|---|---|
| CKDIV8(4) | 7 | Divide clock by 8 | 0 (programmed) |
| CKOUT(3) | 6 | Clock output | 1 (unprogrammed) |
| SUT1 | 5 | Select start-up time | 1 (unprogrammed)(1) |
| SUT0 | 4 | Select start-up time | 0 (programmed)(1) |
| CKSEL3 | 3 | Select Clock source | 0 (programmed)(2) |
| CKSEL2 | 2 | Select Clock source | 0 (programmed)(2) |
| CKSEL1 | 1 | Select Clock source | 1 (unprogrammed)(2) |
| CKSEL0 | 0 | Select Clock source | 0 (programmed)(2) |
Note:
- The default value of SUT[1:0] results in maximum start-up time for the default clock source. See Table. Start-up times for the internal calibrated RC Oscillator clock selection in Calibrated Internal RC Oscillator of System Clock and Clock Options chapter for details.
- The default setting of CKSEL[3:0] results in internal RC Oscillator @ 8MHz. See Table 'Internal Calibrated RC Oscillator Operating Modes' in Calibrated Internal RC Oscillator of the System Clock and Clock Options chapter for details.
- The CKOUT Fuse allows the system clock to be output on PORTB0. Please refer to Clock Output Buffer section in the System Clock and Clock Options chapter for details.
- Please refer to System Clock Prescaler section in the System Clock and Clock Options chapter for details.
The status of the Fuse bits is not affected by Chip Erase. Note that the Fuse bits are locked if Lock bit1 (LB1) is programmed. Program the Fuse bits before programming the Lock bits.