If you are looking for processors that are intellectually challenging, consider looking at Analog Devices DSPs (blackfin) and Texas Instruments (MPS430).
Just curious what makes them any more "intellectually challenging" than any other processor/processor family. I can see that flipping to a DSP might be a little different, maybe, but the MPS series is just another MCU. Thoughts?
I meant because of the DSP functionality. Also in my (limited) experience, black fins are often used with lots of external devices, threading, processing, memory, etc so there are lots of challenges to consider. Whereas small MCUs are often just doing a few simple tasks with limited externals. There are certainly other “intellectually challenging” mcus just that these seem to be industry leaders.