Learning Challenge - 6502 Assembly: Day 10-11

Day 10 was kind of a dud. I was more worried that I was losing my main OS drive on my computer, so I didn't do a learning challenge. (Everything's fine, AFAICT).

Day 11 and I decided to try something a little different:

Playing around with Mac/65 on an Atari XEGS

This is a reproduction cartridge of the venerable (and awesome) Mac/65 cartridge from Optimized Software Solutions; makers of some of the best development tools for the Atari. (Available here.) I have it plugged into an Atari XEGS (with some of the best composite video of any Atari machine).

What I was trying in this iteration was to see if I could copy the data in the memory locations for one of the controllers over to the X and Y registers. So the X register would hold the value of the joystick and the Y register would hold the value of the joystick trigger. This was mimicking some of the input / output routines that Assembly Lines was doing with the Apple machines that I wanted to see if I could replicate in some fashion.

Simple? Yes. Pointless? Of course.

Fun? You betcha.

Holding the joystick, trigger not depressed

What you can't see in these images is the (excellent) DDT debugger iterating through the code as I move the joystick. I was only able to capture the trigger getting pushed and released; and that seems to only be showing the JMP instruction at the end.

Holding the joystick, trigger depressed

Not a whole lot learned in this iteration outside of some of the memory mapping of the Atari (the book in the left-hand corner is "Mapping the Atari" from Compute Books, which was the de-facto memory mapping of the Atari machines. (If you want to hear how Ian Chadwick mapped out the Atari check out the Antic Podcast interview.)


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