Part Number: MSP430F5438
We are implementing the Modbus in our design wherein the requirement is to support the Modbus speed of 38400 baud. Currently we are using ACLK of 32.768KHz for MSP430 which can reasonable bit-slice up to 9.6K baud. To support 38.4Kbps baud rate in UART, crystal frequency has to be selected accordingly.
By theory UART clock needs to have 16X greater than the Baud rate, which means UART frequency has to be min 614.4Kbps (38.4 kbps X16) wherein the crystal frequency comes to 9.83040MHz to achieve the desired baud rate. However such high frequency clock may likely to impact the EMC performance. Hence need to know the exact clock requirement for MSP430 UART to achieve this baud rate to avoid any errors in communication.(variation due to crystal tolerance, jitter ignored).
As per SLA0049 application note, it is found that we can use MCLK of 1.048MHz to generate UART baud rate of 38.4Kbps. Does this mean that we need to use this crystal frequency? Please confirm.
Also what change needs to be done in SW to handle this change?
Thanks,
Ajit
