Content originally posted in LPCWare by eamonnh on Fri Aug 08 03:02:06 MST 2014
Hi Scottreed,
I've run comms between a pair of 43xx at 51MHz using an oversampling ratio of 4. Seemed rock-solid. However, I think a ratio of 6 is preferable for more robustness and reliability. Even Uart1 has an OSR register even though it's not declared in the docs. I often use Uart1 as a console @ 3MHz driven from the 12MHz IRC, with oversample of 4. (Allows me to change CPU frequency freely without having to worry about console.)
I believe that anything from 34MHz down is pretty robust but it would need testing in your application to see if the waveforms arrive sufficiently undistorted to deliver reliable comms.
The NXP UARTs are really well-engineered peripherals.
Kind regards - Eamonn