Z80 Telescope Controller (was Homebrew newsgroups / forums?)

gtulloch at shaw.ca gtulloch at shaw.ca
Wed Oct 26 23:36:51 CDT 2005

Well, ok, in that case ...

I'm building a Z80 based microcontroller as a telescope controller, to 
run a few stepper motors, calculate and correct for periodic errors as 
well as XYZ errors in the mount. The driver circuit is done 
(http://www.bbastrodesigns.com/cot/steppercircuit.html), and 
currently runs off a DOS app which uses the parallel port to pulse 
the motor windings. However, I prefer not to use a dedicated
DOS PC so I'd like to put a Z80 in front of the driver with an RC 
circuit connected to the NMI so I know how long the duration between 
interrupts is and can thus calc the steps required to track. For historic
reasons the code will be written in FORTH - a PC connected via serial
will do all the heavy lifting as far as telling the Z80 where to point 
and how. Comments on the veracity of this architecture welcome!

I have a few questions I'm hoping someone can answer for me, starting 
with the following: I have a Z80A and a 4 mhz TTL clock 
oscillator - I'm wondering if it would be ok to connect the clock 
directly to the CPU or is it wise to connect it via a parallel or 
serial resonant oscillator circuit like those described here:


Why be so elaborate? The data sheets for the oscillator doesn't say 
"Make sure you connect via a parallel or serial resonent oscillator 

Thanks for any light you can shed on this, Google hasn't been helpful.
I have references that do it both ways without explanation so I'm 


cctalk-bounces at classiccmp.org wrote on 26/10/2005 09:25:58 PM:

> Gord wrote...
> > I'm building a Z80 based computer as a stepper motor controller, and 
> > would be nice if there was a homebrew newsgroup to ask questions on 
> > I don't think this is the group to do so - any recommendations?
> Um... I would certainly think developing a new system around a classic 
> processor (Z-80) is certainly ok on this group :)
> Jay 

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