[Coco] CoCo/PC hybrid....

Frank Swygert farna at att.net
Mon Sep 14 21:44:15 EDT 2009

Okay, I never have been much of a programmer, and really done little 
more hardware than a few kits and mods to existing hardware, but I've 
been thinking too much!

One of you programming guys take a look at the resources on this site: 
I've been comparing the pin-out of a parallel port to that of the CoCo 
expansion port. I'm almost convinced that it would be relatively cheap 
and easy to make a small converter board that would plug into a standard 
parallel port and take a CoCo cartridge. Might have to add a source of 
external power, but that could be a cord that goes back into the PC case 
and plugs into a drive connector. Hey, even move +12V out there! The 
goal would be to use cartridges for data transfer purposes or to 
build/use an inexpensive I/O board. Throw the cartridge compatibility 
out and just make it a multi-purpose/experimenter's I/O board with a 
wire-wrap header and I think it gets cheaper and easier. Limit the goal 
to a data I/O board that could be programmed from Nitros9 or DECB and 
forget the cartridge connector and things get easier!

The real headache I see is the 13 address lines. There would have to be 
some kind of decoding done on the board so that only a couple lines on 
the parallel port could be used for decoding. But then again if you 
throw away direct cartridge compatibility and use it strictly for data 
I/O, is that much address decoding really necessary? Told you I wasn't 
much of a programmer/hardware builder!! 

Programming the port from DECB is my main interest. One thing I always 
liked most about the CoCo was the easy I/O projects and using it as a 
controller. Started to write a digital dash for my car using just the 
serial, cassette, and joystick ports for inputs (mainly the relay on the 
cassette port). Lack of an inexpensive display easy to install in the 
dash stopped me! There are such animals for cars now, but that 
programmable I/O port would sure make a CoCo emulator customized and 
installed in flash memory on a simple single board computer (maybe an 
inexpensive Mini ITX with a VIA 800MHz chip...) a real possibility. The 
older Mini ITX boards are starting to show up on e-bay priced reall 
nicely. Would make a good base for a "CoCo4" (didn't want to use that in 
the subject line though!!). Use a IDE to flash card adapter for the main 
drive, then attach a small IDE laptop drive....

Frank Swygert
Publisher, "American Motors Cars" 
Magazine (AMC)
For all AMC enthusiasts
(free download available!)

More information about the Coco mailing list