ADAU144x Pseudo-random square wave?

I have a possibly strange requirement for a bench test that I am developing. Currently I am switching between two signal lines using an index-selectable MUX. The index is created using a square wave signal of 0.4Hz with an AB in CD out condition block and DSP readback. This works well, switching the MUX inputs at 0.4 Hz intervals. Now I would like to pseudo-randomize this square wave generator to allow a range of values (lets say 0.2Hz-0.8Hz) to switch the MUX. Any ideas how I might do this on the ADAU144x or if it's even possible?

Thanks!