Make pin mux decisions before starting schematics (at block diagram level)
External Bus Selection Register (EBSR) controls 2 serial port pin muxes and 1 parallel port pin mux with software
Software can change pin mux mode during execution, but affected peripherals must stop clocks before and reset after the change PPMODE selection (no mixing PPMODEs)
It is recommended to set the EBSR register only once after bootloader completion. The EBSR logic is asynchronous and can cause unexpected behavior on pins being muxed (glitches, driven states, and so forth).