HP41C with Rp Pico attached

[MeindertKuipers]

Good work Thomas!

I am making some progress as well using the PIO in the RP2040 to handle the low level HP41 interfacing. A bit of a challenge but a first level simple ISA bus tracer is working quite well with some refinements still to be done. There are some complications that needed to be solved and I can hint that handling the PWO transitions is necessary. I can also add that in some cases the exact signal assignment is important. Next is to add handling address and driving ISA for ROM and QROM emulation.