DIY Top Octave Dividers

Joachim Verghese jocke at netcontrol.fi
Fri Nov 5 12:39:18 CET 1999


WeAreAs1 at aol.com wrote:

> Each 8253 contains three separately addressable 8-bit counters, so you
> would need four IC's to get all twelve semitones.

I think they're 16-bit, actually.

> If you needed output levels higher than TTL levels, you could add a
> couple of hex level-shifting buffer IC's (such as the 7417 15volt
> open-collector buffer/driver).

Yes, you'd have to include level shifters, and a local 5V regulator.
I guess a single-chip solution is out of the question. :-(

> Joachim, are you sure that a 9-bit counter is needed to get the exact
> pitch ratios?

Seeing as most of the division ratios of the 50240 are higher
than 256 (but lower than 512), I reckon 9-bit counters are required.
And the fact that the outputs of the 50240 are 50% square waves
complicates matters further, as some of the ratios are odd
numbers.

-joachim




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