The AVR instruction set is reasonably nice for hand-coding (and has a more modern feel to it than the 'HC11, which may be relevant if you're using it as a teach

The AVR instruction set is reasonably nice for hand-coding (and has a more modern feel to it than the 'HC11, which may be relevant if you're using it as a teaching example). I haven't used PICs since the PIC14 days; it was a painfully minimalist ISA like the 6502; the newer PICs are better, I gather. The ARM set isn't unpleasant but it's definitely a modern set designed as a compiler target rather than for hand coding, and most ARM chips are large enough there's no real reason not to use a compiler for almost all the code.