My C4P Project

[Steve Gray]

Recently I've been learning Kicad. I've made a couple boards that I'm waiting to get back from the PCB house. In the mean time I thought I might sharpen my Kicad skills and start working on something that I've been thinking about for a long time... A new C4P compatible computer on a single board... Superboard-C4P. Looking at all the boards it appears that the 540B video board is the most complicated, filled with lots of ttl chips for timing and decoding etc. So I started transfering the schematic sheets into Kicad. Along the way I've been making some minor modifications to reduce the parts count and to add some functionality.

I'm replacing the 8T chips (pairs) with one 'LS245's, the 2114's with 64K skinny dip's and character rom with 64K EPROM. I also expanded the control register from 4 bits to 8.
Right now I have all the components entered and am about to check my wiring etc. Here it is:

Draft Schematic 540B

540B-2016-05-18.png (226.18 KiB) Viewed 8483 times

There are so many TTL chips... The address decoding and video counters take up the bulk of the board. The address decoding might be reduced by using a PLA chip (or eprom simulating one). The video counters are basically what you would find in a chip like the 8645 CRTC controller chip. I've considered using that but there would be a problem... the control register controls switching from 32 to 64 columns with a single POKE but I don't think I could replicate that with a CRTC chip (is this really a concern?). I also added an RGBI output which should make converting the video to HDMI much easier.

Eventually I want to incorporate the other boards, which shouldn't be as difficult as the 540B board. I want to add the floppy controller and eventually make a PCB that could fit into a small keyboard-sized case (I'm thinking C64 or C128 case as I have lots of spares).

I'm still learning electronic design, but I've been studying various vintage computer schematics to understand how things work. I hope I haven't taken on something too big

Thoughts?
Steve

[glitch]

Good work so far! You might look into breaking up the schematic into several sheets -- I see you've used global nets which means you can break up the schematic and the nets will stay connected. Makes it easier to digest when you have it separated into a number of sheets by related function. This is how OSI did it in their original schematics, e.g. the 510 board.

[Steve Gray]

Good work so far! You might look into breaking up the schematic into several sheets -- I see you've used global nets which means you can break up the schematic and the nets will stay connected. Makes it easier to digest when you have it separated into a number of sheets by related function. This is how OSI did it in their original schematics, e.g. the 510 board.

Thanks! Well, actually I do have multiple sheets, but only one for each subsection. The video is on one. The cpu will be another, the FDC another etc. I like to be able to see the entire schematic so I can get an overall picture. I guess as I progress I might have to change that though.

Steve

[dave]

Steve, this is awesome! Can't wait to see how it turns out!

Dave

[Steve Gray]

Steve, this is awesome! Can't wait to see how it turns out!

Dave

I think the C4P's video capabilities are what attracted me to the computer. That and all the ports on the back.
I'd like to cram as much from the original system in as i can, and perhaps throw in some other goodies, like an AY sound chip, swichable basic, ram under rom, atari compatible joystick ports, etc ( ideas are welcome). I'd love to add some type of sd card disk system but that might be pushing it...

It will depend on how much board space and time i have.

Steve

[Steve Gray]

Not much progress to report... still planning things. However, since I was in an OSI mood I decided to make a small project webpage:

http://www.6502.org/users/sjgray/projec ... index.html

Right now it's just a place to put thoughts, schematics, links, etc. There is a pdf of my 540B board that's a lot cleared than I posted here.

As always, thoughts, feedback, suggestions are always welcome.

Steve

[Jeff]

Awesome project!