Subject:
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Re: Main ROM routine
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Newsgroups:
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lugnet.robotics
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Date:
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Thu, 12 Nov 1998 11:30:13 GMT
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Original-From:
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Ben Laurie <ben@algroup.co/StopSpam/.uk>
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Viewed:
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2511 times
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Kekoa Proudfoot wrote:
>
> > Kekoa Proudfoot wrote:
> > > To adjust the PWM, you need to override the motor part of the OCIA routine,
> > > which is hardcoded to rotate a single byte per motor, using the LSB to
> > > modulate two control bits stored elsewhere using a 1 ms waveform. Servo
> > > control will therefore be slightly more difficult to do, as servos require
> > > accurate pulses in the 1-2 ms range, if I remember correctly.
This bit was me, for the record:
> > So is f000 the memory-mapped motor drivers? If I've understood it, efca
> > contains the direction bitmaps (10 for one way, 01 for the other,
> > 11xx2233 is the byte layout, if you see what I mean), f000 and efce are
> > the same layout, but modulated by efcb-efcd (which do the PWM,
> > effectively). efce gets set up with the _next_ value, and f000 is the
> > actual hardware. Right?
>
> Memory-mapped motor drivers, yes. A strange way to do things. But f000 is
> only written and never read, so it must be that way.
Not that strange - when I worked on embedded systems, we often did this.
When you get down to it, from the electronics point of view, the
difference between I/O and memory is typically just 1 signal line and
the number of significant address bits. The advantage for firmware is
often that there are far more ways to address memory than I/O ports,
though it hardly seems to matter in this case. It may even be that
they've only bothered with a partial decode, in which case, you may find
that f0xx works, too.
Cheers,
Ben.
--
Ben Laurie |Phone: +44 (181) 735 0686| Apache Group member
Freelance Consultant |Fax: +44 (181) 735 0689|http://www.apache.org/
and Technical Director|Email: ben@algroup.co.uk |
A.L. Digital Ltd, |Apache-SSL author http://www.apache-ssl.org/
London, England. |"Apache: TDG" http://www.ora.com/catalog/apache/
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Message is in Reply To:
 | | Re: Main ROM routine
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| (...) Memory-mapped motor drivers, yes. A strange way to do things. But f000 is only written and never read, so it must be that way. -Kekoa (26 years ago, 12-Nov-98, to lugnet.robotics)
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