Question: How should I select the clock to PSoC 3 UART? What is the relationship between baud rate and the clock and what are the accuracy requirements?
Answer: There are two main points to consider while setting the clock to the UART component.
1. When the external clock option is selected for the UART component, the clock should be 8 times the baud rate. For example:
For a baud rate of 19.2kbps, the clock should be 153.6KHz
For a baud rate of 115.2kbps, the clock should be 921.6KHz
When internal Clock option is selected, the PSoC Creator automatically configures the clock input to the UART based on the baud rate selected.
2. The tolerance for the UART clock for error free communication is about 4%. The IMO provides 1% tolerance at 3MHz and 2% tolerance at 6MHz. So, the clock to the UART may be generated from 3MHz or 6MHz IMO. The IMO can also be passed through the PLL and can form the clock source for the UART.