Video Update
I’ve been distracted by some other projects, and haven’t made as much progress on BMOW as I’d like. They were interesting distractions, at least: I worked on a crystal radio project with my daughter, and did some brainstorming about a completely new home-built computer design. I did manage to finish about 25% of the video system wiring, though, and I’m almost at the point where I can test for correct operation of the HSYNC and VSYNC signals. If I can find more time this weekend, and I don’t run out of wire, I should be able to tackle most of what’s left.
Hey! Good job getting some of the video system wired. I have a couple questions. I FINALLY started working on my CPU yesterday, and I’ve run into a problem. First off, let me introduce the basics of the alu:
(8 bits come in for the A input, 8 bits for B input, and 3 bits for the instruction)
1) The instruction is sent to a decoder.
2) The decoder sends its outputs through transistors, which turn the chips for different functions on or off. (Say, the Adding/subtracting section has all of its power tied to a transistor’s output, connected to the decoder’s first output)
3) The functions do their job, if turned on.
4) The outputs are sent to the output of the ALU, which will be 8 bits.
http://www.hergesgames.com/ALU.jpg
OK, now would this work, and how would I handle the jumps and copies? Any thoughts on a good idea for a circuit for them? Forgot to add, there will be a 9th bit on each input (A and B) to specify if it is negative or positive. 1=negative, 0=positive.
Woops, also need a set command to set an address in memory to a number.
Brandon, I sent you some suggestions by email.
Phase one of the video system wire-wrapping is finished! This must be the slowest wire-wrapping job ever, but between robots, the Olympics, and other distractions, it’s been hard to find time for it. I’ve finished all the wire-wrapping except for the character generator ROM, but I should be able to draw graphics mode images.
All that’s left now is to solder the VGA connector wires, double-check the connectivity to make sure I didn’t short anything, and then try it out! Hopefully I’ll get a first test tonight.