Can you please provide details about your application like why as such you need to change the no. of data bits.
This link may be useful-
In my application, I have a multiplexer configured via a register. According to my register I can receive data with 8 bits and 9 bits transmitted between start and stop, data send to the same UART (I haven't enouth UDB to had a new one..). That is why I need to change the Data bits value in my code.
In UDB based UART component as available in PSOC3,it is not possible to change the Data bit value in firmware once you set one value for data bit in configuration settings of the component
Ok, thanks for your help !