Baud Rate Calculation Example

The following table shows calculations of CD to obtain a baud rate at 38,400 bit/s for different source clock frequencies. It also shows the actual resulting baud rate and the error.

Table 8-19. Baud Rate Example (OVER = 0)
Source Clock

(MHz)

Expected Baud Rate

(bit/s)

Calculation ResultCDActual Baud Rate

(bit/s)

Error
3,686,40038,4006.00638,400.000.00%
4,915,20038,4008.00838,400.000.00%
5,000,00038,4008.14839,062.501.70%
7,372,80038,40012.001238,400.000.00%
8,000,00038,40013.021338,461.540.16%
12,000,00038,40019.532037,500.002.40%
12,288,00038,40020.002038,400.000.00%
14,318,18038,40023.302338,908.101.31%
14,745,60038,40024.002438,400.000.00%
18,432,00038,40030.003038,400.000.00%
24,000,00038,40039.063938,461.540.16%
24,576,00038,40040.004038,400.000.00%
25,000,00038,40040.694038,109.760.76%
32,000,00038,40052.085238,461.540.16%
32,768,00038,40053.335338,641.510.63%
33,000,00038,40053.715438,194.440.54%
40,000,00038,40065.106538,461.540.16%
50,000,00038,40081.388138,580.250.47%

The baud rate is calculated with the following formula:

Baud rate = MCK / CD × 16

The baud rate error is calculated with the following formula. It is not recommended to work with an error higher than 5%.

Error=1Expected Baud RateActual Baud Rate