The formula given for fBAUD calculates the average frequency over 65536 fref cycles. Although the BAUD register can be set to any value between 0 and 65536, the actual average frequency of fBAUD over a single frame is more granular. The BAUD register values that will affect the average frequency over a single frame lead to an integer increase in the cycles per frame (CPF)
where
Table 1 shows the BAUD register value versus baud frequency fBAUD at a serial engine frequency of 48MHz. This assumes a D value of 8 bits and an S value of 2 bits (10 bits, including start and stop bits).
BAUD Register Value | Serial Engine CPF | fBAUD at 48MHz Serial Engine Frequency (fREF) |
---|---|---|
0 – 406 | 160 | 3MHz |
407 – 808 | 161 | 2.981MHz |
809 – 1205 | 162 | 2.963MHz |
... | ... | ... |
65206 | 31775 | 15.11kHz |
65207 | 31871 | 15.06kHz |
65208 | 31969 | 15.01kHz |