Re: [CAD_CAM_EDM_DRO] Hardware step generator idea

Yes, I was thinking the same and plan to play with that single channel
prototype setup this evening!

I did some heavy duty 8253-speaker hacking around 10 (gosh was it
really that long) year ago...

I'm going to use it in mode 2, where you load a 16 bit count and it
repeatedly counts down from that to 0, generating a single-count
low-going pulse. The PC speaker clocks the device at bit over 1mhz,
but versions are available up to 10mhz. 1mhz gives 10% resolution at
up to 100khz step rate, 10mhz gives 1% resolution at 100khz.

It appears that you can reload the counter start register while it is
running, and it will take effect cleanly on the next cycle. I think I
can probably switch to a one-shot mode for producing discrete pulses
at low speed (ie, less than one pulse per cycle of the update loop).

Chris

> hmmm...
> youve already got a single channel prototype of the hardware
> use a couple bits on the parallel port for direction and enable
> and the PC speaker is driven with an 8254 with gated output
> should be enough for testing
>
> the rest is in software,there is plenty of old source code for the
> PC speaker floating arround that will still run on the newest chipsets
>
> Brian
>
> On Monday 21 May 2001 04:46, you wrote:
> > It seems to me that this card could take the form of an 8254
> > programmable timer (3 channels) running from a suitably fast clock
> > source and something (74hc373, 8255) to provide bits for the direction
> > signal. (Software might also need to control the 8254 gate output when
> > zero speed is commanded)
> > Chris

--
Christopher C. Stratton, stratton@...
Instrument Maker, Horn Player & Engineer
22 Adrian Street, Somerville, MA 02143
http://www.mdc.net/~stratton
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