Teaching kids about computers...

Tony Duell ard at p850ug1.demon.co.uk
Wed Nov 28 18:16:52 CST 2007

> >  A Color Computer or Color Computer 2 seems to fit the bill.  The CPU is
> > the nicest of the 8bits (IMHO) and the video screen is more logical than
> > anything you'll find on the C64, Atari or Apple.
> >
> >  You can even do multichannel sound, but that tends to suck up the CPU 8-)
> I'd tend to agree.  The 6809 is a lovely processor, and there aren't any of

I also suggested it before reading the rest of the thread. The 6809 is 
probably the easieest 8-biotter to learn. 

> the "black box" chips that others have mentioned.  The video is generated by
> a Motorola 6547 -- simple bitmap (except for the "semigraphics" modes) and

I think you mean 6847 here.

In any case the video is geenrated by a combination of the 6883 SAM (which
adderesses the main meory) and the 6847 VDG (which turns the data read from
RAM into the video signal). IIRC, the semigraphics mode come from programming
the SAM for graphics and the VDG fro text.

> no sprites.  No specialized I/O hardware to decipher; the serial port is
> bitbanged directly by the CPU.

The I/O is very simple. 2 6821 PIAs. One essentially scans the keyboard. 
The other cotnrols the VDG, drives the DAC (used for sound, cassette out, 
and joustick ports), and handles bit-banged I/O to the cassette and 
serial ports. 

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