[Coco] [Color Computer] Happy New Years!

[Roger Taylor]

At 02:43 PM 1/3/2008, you wrote:
>Phil <phil.salathe at gmail.com> wrote:
>
> > >BTW: There is no reason to record 44.1 khz stero for this. 11.025 khz
> > >mono would be fine.
> >
> > Interesting -- so the bandwidth of the Coco cassette data signal only
> > goes up to 5.5kHz or so?  I guess it stands to reason.
>
>The CoCo documentation says it uses a single 1200 hertz sinusoidal wave
>for a zero bit and a single 2400 hertz sinusoidal wave for a one bit.
>
>But I did some measurements from real hardware recently and found the
>real frequency is 1094.7 and 2004.5 hertz.


Perhaps the 2004.5 hz is due to slight timing differences but it 
falls into the safe zone for the syncing opcodes.  I'm not sure how 
1094.7 hz works when it should be ~1200 hz, but a better look at the 
instructions could reveal if the "other" waveform is actually being 
pumped at half or double the rate of the original waveform.  The 
sinewave is there in the ROM code but maybe the delay opcodes didn't 
consider overhead or something.