Answer: The CSD user module uses all or few of the VC1, VC2 and VC3 clock dividers depending on the device used (CY8C21x34 or CY8C24x94). The value of these dividers get configured according to the Scan Speed and Resolution parameters selected in the CSD user module parameters. When you use the VC1, VC2 and VC3 dividers to generate the clock to the UART, TX8 or RX8 user module, the CSD user module API code overwrites the clock dividers when the CSD_Start function is called. Following are some of the options that may be used to implement CSD and UART in the same project.
Options to implement CSD + UART in CY8C21x34
- Use the CSDADC, Counter16, TX8SW and RX8. The CSDADC uses one digital block, Counter16 uses two digital blocks and RX8, one digital block. The TX8SW is a software implementation of the serial transmitter and does not use any digital block. Use the Counter16 to divide SysClk and generate the clock for the RX8 block.
- If the desired baud rate is 19.2kbps or above, the desired clock for UART can be generated using an 8 bit counter dividing the 24MHz SysClk. In this case, you can use Counter8, and the UART user module together.
- If the Scan speed of the CSD is going to remain unchanged, then find out the VC1 divider value corresponding to the scan speed from the CSDADC user module data sheet. Then use VC1 as the clock source to the Counter8. Using this method, baud rates of less than 19.2kbps can be generated using Counter8.
Options to implement CSD + UART in CY8C24x94
- In CY8C24x94 device, CSD uses only the VC1 clock divider. VC2 and VC3 are free to be used. Depending on the Scan speed, VC1 divider may be set to 2, 4, or 8 by the CSD user module. Find out this divider value from the user module data sheet and set VC2 and VC3 dividers accordingly to generate the clock for the UART
- Use PRS8 for CSD. This configuration uses only one digital block and you can use Counter16 / TX8SW / RX8 combination or Counter8 / UART combination (similar to #1, #2 and #3 described for CY8C21x34 above) to implement CSD + UART.