for the normal mode: baud = fosc/(16*(UBRR+1)) for the double speed mode : baud = fosc/(8*(UBRR+1)) with UBRR being the 12bit divisor in the baud rate register
for the div 64 mode: baud = fosc/(64*(n+1)) for the div 16 mode : baud = fosc/(16*(n+1)) for the div 4 mode : baud = fosc/(4*(n+1)) with n being the divisor
Error = ((actual baudrate / declared baud rate)-1 )*100; // in percentThe table list the absolute error in the baudrate in percent. A "-" indicates the frequency cannot be achieved with sufficient accuracy.
baud rates quartz frequencies |
300 | 600 | 1200 | 2400 | 4800 | 9600 | 19.2k | 38.4k | 57.6k | 115.2k | 250k | 500k | 1M |
20MHz div8 | - | - | 0 | 0 | 0.1 | 0.2 | 0.2 | 0.2 | 0.9 | - | 0 | 0 | - |
20MHz div16 | - | 0 | 0 | 0.1 | 0.1 | 0.2 | 0.2 | 1.7 | - | - | 0 | - | - |
18.432MHz div8 | - | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | - | - | - |
18.432MHz div16 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | - | - | - |
16MHz div8 | - | 0 | 0 | 0 | 0.1 | 0.2 | 0.2 | 0.2 | - | - | 0 | 0 | 0 |
16MHz div16 | 0 | 0 | 0 | 0.1 | 0.1 | 0.2 | 0.2 | 0.2 | - | - | 0 | 0 | 0 |
14.7456MHz div8 | - | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | - | - | - |
14.7456MHz div16 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | - | - | - |
11.0592MHz div8 | - | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | - | - | - |
11.0592MHz div16 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | - | - | - |
8.0MHz div8 | 0 | 0 | 0 | 0.1 | 0.1 | 0.2 | 0.2 | 0.2 | - | - | 0 | 0 | 0 |
8.0MHz div16 | 0 | 0 | 0.1 | 0.1 | 0.1 | 0.2 | 0.2 | 0.2 | - | - | 0 | 0 | - |
7.3728MHz div8 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | - | - | - |
7.3728MHz div16 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | - | - | - |
6.0MHz div8 | 0 | 0 | 0 | 0.1 | 0.1 | 0.2 | 0.2 | - | 0.2 | - | 0 | - | - |
6.0MHz div16 | 0 | 0 | 0.1 | 0.1 | 0.1 | 0.2 | - | - | - | - | - | - | - |
4.91MHz div8 | 0 | 0 | 0.1 | 0.3 | 0.7 | 1.5 | - | - | - | - | - | - | - |
4.91MHz div16 | 0 | 0 | 0.3 | 0.7 | 1.5 | - | - | - | - | - | - | - | - |
4.19MHz div8 | 0 | 0 | 0.1 | 0.1 | 0.1 | 1.0 | 1.0 | - | 1.0 | - | - | - | - |
4.19MHz div16 | 0 | 0 | 0.1 | 0.1 | 1.0 | 1.0 | - | - | - | - | - | - | - |
4.0MHz div8 | 0 | 0 | 0.1 | 0.1 | 0.1 | 0.2 | 0.2 | 0.2 | - | - | 0 | 0 | - |
4.0MHz div16 | 0 | 0 | 0.1 | 0.1 | 0.1 | 0.2 | 0.2 | - | - | - | 0 | - | - |
3.6864MHz div8 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | - | - | - |
3.6864MHz div16 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | - | - | - |
2.0MHz div8 | 0 | 0 | 0.1 | 0.1 | 0.1 | 0.2 | 0.2 | - | - | - | - | - | - |
2.0MHz div16 | 0 | 0 | 0.1 | 0.1 | 0.1 | 0.2 | - | - | - | - | - | - | - |
1.8432MHz div8 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | - | - | - |
1.8432MHz div16 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | - | - | - |
1.0MHz div8 | 0 | 0 | 0.1 | 0.1 | 0.1 | 0.2 | - | - | - | - | - | - | - |
1.0MHz div16 | 0 | 0 | 0.1 | 0.1 | 0.1 | - | - | - | - | - | - | - | - |