I'd like to build an Intel 8085 trainer for a final year project. The trainer will be used by students and will basically accept machine code entered by students, load these into RAM and run the code. Students will also be able to single-step through the code, examine memory and registers, all basic functions of a trainer. There will also be GPIO (for LEDs and such) on-board as well as some other components (LCDs, seven-segs) you might find on a dev board. A touchscreen would be a nice touch, for input and display. There should also be the option of power using cheap batteries, since electricity isnt at all reliable here. All on a PCB with packaging etc.
I've done a bit of research and thinking and concluded that there are 3 main ways I could do this:
- Get a PIC18 (or some other MCU) and program it to understand and execute all machine code input. Basically the PIC18 will emulate an 8085.
- Get a PIC18 and an 8085. Let the PIC18 serve as a monitor and control everything except running the user code.
- Get an 8085 and let it do everything from running user code to blinking LEDs on-board. Use EPROM to store the monitor code.
I have other school work that will occupy a lot of my time and it takes a month at least for ordered components to get to me (when they do), so I wont have as much time as I'd like. So I'm inclined to go with the 2nd option since it saves me the work of having to delve too deeply into the 8085 instruction set and all the associated assembly programming, which is something I barely know. Plus I think its also efficient, since it lets the 8085 do what it does best and lets the PIC handle the rest. My main aim is straight-forward (i.e. least effort :)) and effective. I'll be using 6116 for RAM and the usual 74373 for address latching. Not sure what chip to use for I/O yet (I/O-mapped I/O).
What I'd like to know is:
- Is this option really as straight-forward as it seems? Any pitfalls I should be aware of?
- Is there a better way? Maybe one not among my listed options?
- How feasible is battery power with 9 V batteries? Any better cheap alternative?
- Any advice on input? I'd like to use a resistive touchscreen and not buttons to give a modern feel (like this 7-inch TFT) but i'm worried about all the extra pin usage and if it will even be big enough? Maybe just use pushbuttons for input and use a far smaller screen for display alone?
- Any general advice on the whole thing?
Thanks in advance.