My C4P Project
Posted: Thu May 19, 2016 12:06 am
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:
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
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:
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