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Groups > comp.lang.forth > #19142

Re: Parallax Propeller

From Walter Banks <walter@bytecraft.com>
Newsgroups comp.lang.forth, comp.arch.embedded
Subject Re: Parallax Propeller
Date 2013-01-25 11:49 -0500
Organization Aioe.org NNTP Server
Message-ID <5102B7B1.C1FE8CC2@bytecraft.com> (permalink)
References (5 earlier) <e1zIs.2586$Ow3.1870@viwinnwfe02.internal.bigpond.com> <qvvjf81u8h341ng3ndmnq48egqhqjf5r9f@4ax.com> <7xwqv9m2ub.fsf@ruckus.brouhaha.com> <9ejmf8hp8uf95n8ot7fqq3tv80tkb2cf7o@4ax.com> <20130124232504.16848.3314@localhost.localdomain>

Cross-posted to 2 groups.

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None wrote:

> rickman <gnuarm@gmail.com> writes:
> > If you read Chuck Moore's blog he spent some time trying to implement a
> > video output without a clock.  He only gave up that idea when he found
> > the pixels jittered on the screen because of the vagaries of async
> > processor timing loops.
>
> I played with the PropTerm and found that the CPU-generated VGA bit stream (a
> CPU got dedicated to the task) resulted in displays which always had a little
> bit of fuzziness.  It worked, and was quite readable, but the sharpness
> of a regular PC display really made me aware of the limits of a pure software
> approach to analog generation.
>

I have worked on a couple event driven ISA designs. Jitter is visible
on displays but it is equally problematic with control systems. The best solution

that I have seen/used is to have the hardware transfer out a precomputed
value or latch an input on the event interrupt trigger. Output values are
almost always known in advance.

This minor change has essentially little impact on the processor silicon
complexity.

A second important performance issue is to have an easily accesses data
area associated with each interrupt source. It means that a lot of common
code (pwm, ac phase control... ) can be a single executable. In some cases
preloading an index register with the start of data for that interrupt in some
hardware has significant performance improvements.

Walter Banks
Byte Craft Limited

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Thread

Parallax Propeller Peter Jakacki <peterjakacki@gmail.com> - 2013-01-13 06:37 +0000
  Re: Parallax Propeller MK <mk@nospam.co.uk> - 2013-01-13 10:26 +0000
    Re: Parallax Propeller Peter Jakacki <peterjakacki@gmail.com> - 2013-01-13 12:22 +0000
      Re: Parallax Propeller Andrew Haley <andrew29@littlepinkcloud.invalid> - 2013-01-13 07:24 -0600
        Re: Parallax Propeller Peter Jakacki <peterjakacki@gmail.com> - 2013-01-13 13:55 +0000
          Re: Parallax Propeller mhx@iae.nl (Marcel Hendrix) - 2013-01-13 17:13 +0200
            Re: Parallax Propeller Andrew Haley <andrew29@littlepinkcloud.invalid> - 2013-01-16 06:23 -0600
              Re: Parallax Propeller Peter Jakacki <peterjakacki@gmail.com> - 2013-01-16 15:01 +0000
                Re: Parallax Propeller Andrew Haley <andrew29@littlepinkcloud.invalid> - 2013-01-16 09:12 -0600
                Re: Parallax Propeller Peter Jakacki <peterjakacki@gmail.com> - 2013-01-16 15:36 +0000
                Re: Parallax Propeller Andrew Haley <andrew29@littlepinkcloud.invalid> - 2013-01-16 10:59 -0600
                Re: Parallax Propeller Peter Jakacki <peterjakacki@gmail.com> - 2013-01-16 23:38 +0000
                Re: Parallax Propeller Andrew Haley <andrew29@littlepinkcloud.invalid> - 2013-01-17 04:04 -0600
                Re: Parallax Propeller Mark Wills <forthfreak@gmail.com> - 2013-01-17 04:52 -0800
                Re: Parallax Propeller Hugh Aguilar <hughaguilar96@yahoo.com> - 2013-01-24 22:48 -0800
                Re: Parallax Propeller Mark Wills <forthfreak@gmail.com> - 2013-01-24 23:10 -0800
                Re: Parallax Propeller Hugh Aguilar <hughaguilar96@yahoo.com> - 2013-01-28 17:42 -0800
                Re: Parallax Propeller "Rod Pemberton" <do_not_have@notemailnotz.cnm> - 2013-02-05 06:05 -0500
                Re: Parallax Propeller Andrew Haley <andrew29@littlepinkcloud.invalid> - 2013-02-05 08:41 -0600
                Re: Parallax Propeller Paul Rubin <no.email@nospam.invalid> - 2013-02-05 10:21 -0800
                Re: Parallax Propeller Bernd Paysan <bernd.paysan@gmx.de> - 2013-02-05 21:37 +0100
                Re: Parallax Propeller "Elizabeth D. Rather" <erather@forth.com> - 2013-02-05 10:44 -1000
                Re: Parallax Propeller Andrew Haley <andrew29@littlepinkcloud.invalid> - 2013-02-05 15:52 -0600
                Re: Parallax Propeller Paul Rubin <no.email@nospam.invalid> - 2013-02-06 00:29 -0800
                Re: Parallax Propeller Paul Rubin <no.email@nospam.invalid> - 2013-02-06 00:31 -0800
                Re: Parallax Propeller Bernd Paysan <bernd.paysan@gmx.de> - 2013-02-06 19:46 +0100
                Re: Parallax Propeller Paul Rubin <no.email@nospam.invalid> - 2013-02-09 00:11 -0800
                Re: Parallax Propeller anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2013-02-09 10:25 +0000
                Re: Parallax Propeller Hugh Aguilar <hughaguilar96@yahoo.com> - 2013-02-06 18:26 -0800
                Re: Parallax Propeller Hugh Aguilar <hughaguilar96@yahoo.com> - 2013-02-05 15:07 -0800
                Re: Parallax Propeller Hugh Aguilar <hughaguilar96@yahoo.com> - 2013-02-05 15:49 -0800
                Re: Parallax Propeller "Rod Pemberton" <do_not_have@notemailnotz.cnm> - 2013-02-05 06:04 -0500
                Re: Parallax Propeller Hugh Aguilar <hughaguilar96@yahoo.com> - 2013-02-05 15:21 -0800
                Re: Parallax Propeller rickman <gnuarm@gmail.com> - 2013-01-16 18:09 -0500
          Re: Parallax Propeller Ben Bradley <ben_u_bradley@etcmail.com> - 2013-01-18 21:07 -0500
            Re: Parallax Propeller "Paul E. Bennett" <Paul_E.Bennett@topmail.co.uk> - 2013-01-19 10:06 +0000
              Re: Parallax Propeller Arlet Ottens <usenet+5@c-scape.nl> - 2013-01-19 13:04 +0100
              Re: Parallax Propeller "A. K." <akk@nospam.org> - 2013-01-19 13:22 +0100
                Re: Parallax Propeller Bernd Paysan <bernd.paysan@gmx.de> - 2013-01-19 13:38 +0100
              Re: Parallax Propeller David Brown <david.brown@removethis.hesbynett.no> - 2013-01-19 17:12 +0100
                Re: Parallax Propeller albert@spenarnc.xs4all.nl (Albert van der Horst) - 2013-01-19 16:45 +0000
                Re: Parallax Propeller David Brown <david.brown@removethis.hesbynett.no> - 2013-01-20 17:49 +0100
                Re: Parallax Propeller upsidedown@downunder.com - 2013-01-19 20:54 +0200
                Re: Parallax Propeller Paul Rubin <no.email@nospam.invalid> - 2013-01-19 11:04 -0800
                Re: Parallax Propeller upsidedown@downunder.com - 2013-01-19 23:05 +0200
                Re: Parallax Propeller Mark Wills <markrobertwills@yahoo.co.uk> - 2013-01-20 01:05 -0800
                Re: Parallax Propeller Arlet Ottens <usenet+5@c-scape.nl> - 2013-01-20 12:11 +0100
                Re: Parallax Propeller upsidedown@downunder.com - 2013-01-20 13:53 +0200
                Re: Parallax Propeller upsidedown@downunder.com - 2013-01-20 13:26 +0200
                Re: Parallax Propeller Les Cargill <lcargill99@comcast.com> - 2013-01-19 14:23 -0600
                Re: Parallax Propeller Les Cargill <lcargill99@comcast.com> - 2013-01-19 14:18 -0600
                Re: Parallax Propeller David Brown <david.brown@removethis.hesbynett.no> - 2013-01-20 20:32 +0100
                Re: Parallax Propeller Les Cargill <lcargill99@comcast.com> - 2013-01-20 18:08 -0600
                Re: Parallax Propeller Walter Banks <walter@bytecraft.com> - 2013-01-20 17:12 -0500
                Re: Parallax Propeller Mel Wilson <mwilson@the-wire.com> - 2013-01-20 19:19 -0500
                Re: Parallax Propeller Walter Banks <walter@bytecraft.com> - 2013-01-20 21:12 -0500
                Re: Parallax Propeller David Brown <david@westcontrol.removethisbit.com> - 2013-01-21 09:01 +0100
                Re: Parallax Propeller Walter Banks <walter@bytecraft.com> - 2013-01-21 21:11 -0500
                Re: Parallax Propeller upsidedown@downunder.com - 2013-01-22 09:39 +0200
                Re: Parallax Propeller Mel Wilson <mwilson@the-wire.com> - 2013-01-22 10:14 -0500
              Re: Parallax Propeller Waldek Hebisch <hebisch@math.uni.wroc.pl> - 2013-01-20 02:03 +0000
            Re: Parallax Propeller George Neuner <gneuner2@comcast.net> - 2013-01-19 12:29 -0500
              Re: Parallax Propeller rickman <gnuarm@gmail.com> - 2013-01-23 12:29 -0500
                Re: Parallax Propeller Mark Wills <markrobertwills@yahoo.co.uk> - 2013-01-24 14:03 -0800
                Re: Parallax Propeller Hugh Aguilar <hughaguilar96@yahoo.com> - 2013-01-24 22:55 -0800
                Re: Parallax Propeller Mark Wills <forthfreak@gmail.com> - 2013-01-24 23:03 -0800
                Re: Parallax Propeller Coos Haak <chforth@hccnet.nl> - 2013-01-25 20:02 +0100
                Re: Parallax Propeller Hugh Aguilar <hughaguilar96@yahoo.com> - 2013-01-28 17:13 -0800
                Re: Parallax Propeller David Brown <david@westcontrol.removethisbit.com> - 2013-01-29 09:15 +0100
                Re: Parallax Propeller Anders.Montonen@kapsi.spam.stop.fi.invalid - 2013-01-30 12:19 +0000
                Re: Parallax Propeller David Brown <david.brown@removethis.hesbynett.no> - 2013-01-30 21:18 +0100
                Re: Parallax Propeller Mark Wills <forthfreak@gmail.com> - 2013-01-30 22:57 -0800
                Re: Parallax Propeller Alex McDonald <blog@rivadpm.com> - 2013-01-31 10:38 -0800
                Re: Parallax Propeller Mark Wills <forthfreak@gmail.com> - 2013-01-31 12:34 -0800
            Re: Parallax Propeller Paul Rubin <no.email@nospam.invalid> - 2013-01-19 10:42 -0800
              Re: Parallax Propeller bob@bob.com - 2013-01-19 19:56 -0600
                Re: Parallax Propeller rickman <gnuarm@gmail.com> - 2013-01-23 12:40 -0500
                Re: Parallax Propeller None <vandys@vsta.org> - 2013-01-24 23:26 +0000
                Re: Parallax Propeller Walter Banks <walter@bytecraft.com> - 2013-01-25 11:49 -0500
                Re: Parallax Propeller rickman <gnuarm@gmail.com> - 2013-01-25 09:25 -0500
                Re: Parallax Propeller None <vandys@vsta.org> - 2013-01-25 21:57 +0000
                Re: Parallax Propeller rickman <gnuarm@gmail.com> - 2013-01-26 18:07 -0500
                Re: Parallax Propeller Mark Wills <markrobertwills@yahoo.co.uk> - 2013-01-27 00:50 -0800
                Re: Parallax Propeller Andrew Haley <andrew29@littlepinkcloud.invalid> - 2013-01-27 03:30 -0600
                Re: Parallax Propeller Dombo <dombo@disposable.invalid> - 2013-01-27 12:58 +0100
                Re: Parallax Propeller rickman <gnuarm@gmail.com> - 2013-01-28 21:38 -0500
                Re: Parallax Propeller None <vandys@vsta.org> - 2013-01-27 03:09 +0000
                Re: Parallax Propeller rickman <gnuarm@gmail.com> - 2013-01-28 21:51 -0500
                Re: Parallax Propeller None <vandys@vsta.org> - 2013-01-30 02:10 +0000
                Re: Parallax Propeller rickman <gnuarm@gmail.com> - 2013-01-30 18:32 -0500
            Re: Parallax Propeller David Schultz <abuse@127.0.0.1> - 2013-01-20 11:21 -0600
      Re: Parallax Propeller albert@spenarnc.xs4all.nl (Albert van der Horst) - 2013-01-13 16:24 +0000
      Re: Parallax Propeller David Brown <david@westcontrol.removethisbit.com> - 2013-01-14 10:51 +0100
        Re: Parallax Propeller Peter Jakacki <peterjakacki@gmail.com> - 2013-01-16 06:06 +0000
          Re: Parallax Propeller David Brown <david@westcontrol.removethisbit.com> - 2013-01-16 13:43 +0100
            Re: Parallax Propeller Peter Jakacki <peterjakacki@gmail.com> - 2013-01-16 15:27 +0000
      Re: Parallax Propeller Rafael Deliano <rafael_deliano@arcor.de> - 2013-01-15 21:10 +0100
        Re: Parallax Propeller Peter Jakacki <peterjakacki@gmail.com> - 2013-01-16 06:26 +0000
      Re: Parallax Propeller gavino_himself <visploveslisp@gmail.com> - 2013-01-22 06:26 -0800
    Re: Parallax Propeller Peter Jakacki <peterjakacki@gmail.com> - 2013-01-13 12:44 +0000

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