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Groups > comp.arch.embedded > #28322

Re: $0.03 microcontroller

From Philipp Klaus Krause <pkk@spth.de>
Newsgroups comp.arch.embedded
Subject Re: $0.03 microcontroller
Date 2018-11-05 12:41 +0100
Organization solani.org
Message-ID <prpa97$udb$1@solani.org> (permalink)
References (1 earlier) <874ldtp66e.fsf@nightsong.com> <tl1urdtvs2rr7pqkab7o0rgdk7kecok7fs@4ax.com> <87in28nktr.fsf@nightsong.com> <pppg8a$q0u$1@solani.org> <pppjcf$k13$1@dont-email.me>

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Am 12.10.2018 um 09:44 schrieb David Brown:
> On 12/10/18 08:50, Philipp Klaus Krause wrote:
>> Am 12.10.2018 um 01:08 schrieb Paul Rubin:
>>> upsidedown@downunder.com writes:
>>>> There is a lot of operations that will update memory locations, so why
>>>> would you need a lot of CPU registers.
>>>
>>> Being able to (say) add register to register saves traffic through the
>>> accumulator and therefore instructions.
>>>
>>>> 1 KiB = 0.5 KiW is quite a lot, it is about 10-15 pages of commented
>>>> assembly program listing.
>>>
>>> It would be nice to have a C compiler, and registers help with that.
>>>
>>
>> Looking at the instruction set, it should be possible to make a backend
>> for this in SDCC; the architecture looks more C-friendly than the
>> existing pic14 and pic16 backends. But it surely isn't as nice as stm8
>> or z80.
>> reentrant functions will be inefficent: No registers, and no sp-relative
>> adressing mode. On would want to reserve a few memory locations as
>> pseudo-registers to help with that, but that only goes so far.
>>
> 
> It looks like the lowest 16 memory addresses could be considered
> pseudo-registers - they are the ones that can be used for direct memory
> access rather than needing indirect access.
> 

Considering the multi-core variants of the Padauk µCs:
Those adresses are shared across all cores. Each core only has its own
A, SP, F, PC.
How do we handle local variables?

Option 1: Make functions non-reentrant. Requires duplication of code (we
need per-thread copies of functions), and link-time analysis to ensure
that each thread only calls the function implementation meant for it.
Functions pointers get complicated.

Option 2: Use an  inefficient combination of thread-local storage and stack.

Since this is a small µC, we need a lot of support functions, which the
compiler inserts (e.g. for multiplication); of course those are affected
by the same problems.

Philipp

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Thread

$0.03 microcontroller Clifford Heath <no.spam@please.net> - 2018-10-10 12:05 +1100
  Re: $0.03 microcontroller lasselangwadtchristensen@gmail.com - 2018-10-10 16:12 -0700
  Re: $0.03 microcontroller gnuarm.deletethisbit@gmail.com - 2018-10-10 17:51 -0700
    Re: $0.03 microcontroller lasselangwadtchristensen@gmail.com - 2018-10-10 18:56 -0700
  Re: $0.03 microcontroller Paul Rubin <no.email@nospam.invalid> - 2018-10-10 19:29 -0700
    Re: $0.03 microcontroller upsidedown@downunder.com - 2018-10-11 11:39 +0300
      Re: $0.03 microcontroller Paul Rubin <no.email@nospam.invalid> - 2018-10-11 16:08 -0700
        Re: $0.03 microcontroller Philipp Klaus Krause <pkk@spth.de> - 2018-10-12 08:50 +0200
          Re: $0.03 microcontroller David Brown <david.brown@hesbynett.no> - 2018-10-12 09:44 +0200
            Re: $0.03 microcontroller upsidedown@downunder.com - 2018-10-12 21:30 +0300
              Re: $0.03 microcontroller Philipp Klaus Krause <pkk@spth.de> - 2018-10-12 22:06 +0200
                Re: $0.03 microcontroller upsidedown@downunder.com - 2018-10-12 23:45 +0300
                Re: $0.03 microcontroller Philipp Klaus Krause <pkk@spth.de> - 2018-10-13 21:47 +0200
                Re: $0.03 microcontroller upsidedown@downunder.com - 2018-10-14 11:58 +0300
                Re: $0.03 microcontroller Philipp Klaus Krause <pkk@spth.de> - 2018-10-15 08:14 +0200
                Re: $0.03 microcontroller Philipp Klaus Krause <pkk@spth.de> - 2018-11-11 09:27 +0100
                Re: $0.03 microcontroller Klaus Kragelund <klauskvik@hotmail.com> - 2018-12-26 02:23 -0800
              Re: $0.03 microcontroller Philipp Klaus Krause <pkk@spth.de> - 2018-10-15 10:44 +0200
                Re: $0.03 microcontroller Paul Rubin <no.email@nospam.invalid> - 2018-10-15 07:29 -0700
                Re: $0.03 microcontroller Philipp Klaus Krause <pkk@spth.de> - 2018-10-16 09:19 +0200
                Re: $0.03 microcontroller David Brown <david.brown@hesbynett.no> - 2018-10-16 13:48 +0200
                Re: $0.03 microcontroller upsidedown@downunder.com - 2018-10-15 21:34 +0300
                Re: $0.03 microcontroller Philipp Klaus Krause <pkk@spth.de> - 2018-10-16 09:29 +0200
                Re: $0.03 microcontroller Hans-Bernhard Bröker <HBBroeker@t-online.de> - 2018-10-15 21:22 +0200
                Re: $0.03 microcontroller Philipp Klaus Krause <pkk@spth.de> - 2018-10-16 10:00 +0200
                Re: $0.03 microcontroller Hans-Bernhard Bröker <HBBroeker@t-online.de> - 2018-10-16 22:52 +0200
                Re: $0.03 microcontroller gnuarm.deletethisbit@gmail.com - 2018-10-16 14:01 -0700
                Re: $0.03 microcontroller Hans-Bernhard Bröker <HBBroeker@t-online.de> - 2018-10-17 00:03 +0200
                Re: $0.03 microcontroller Clifford Heath <no.spam@please.net> - 2018-10-17 09:22 +1100
                Re: $0.03 microcontroller gnuarm.deletethisbit@gmail.com - 2018-10-16 15:29 -0700
                Re: $0.03 microcontroller David Brown <david.brown@hesbynett.no> - 2018-10-17 00:46 +0200
                Re: $0.03 microcontroller Niklas Holsti <niklas.holsti@tidorum.invalid> - 2018-10-17 09:35 +0300
                Re: $0.03 microcontroller David Brown <david.brown@hesbynett.no> - 2018-10-17 09:31 +0200
                Re: $0.03 microcontroller gnuarm.deletethisbit@gmail.com - 2018-10-17 07:08 -0700
                Re: $0.03 microcontroller Niklas Holsti <niklas.holsti@tidorum.invalid> - 2018-10-17 18:37 +0300
                Re: $0.03 microcontroller gnuarm.deletethisbit@gmail.com - 2018-10-17 10:04 -0700
                Re: $0.03 microcontroller Niklas Holsti <niklas.holsti@tidorum.invalid> - 2018-10-17 23:07 +0300
                Re: $0.03 microcontroller Philipp Klaus Krause <pkk@spth.de> - 2018-10-17 08:23 +0200
                Re: $0.03 microcontroller upsidedown@downunder.com - 2018-10-17 19:43 +0300
                Re: $0.03 microcontroller Philipp Klaus Krause <pkk@spth.de> - 2018-10-17 20:24 +0200
                Re: $0.03 microcontroller George Neuner <gneuner2@comcast.net> - 2018-10-17 11:31 -0400
            Re: $0.03 microcontroller Philipp Klaus Krause <pkk@spth.de> - 2018-11-05 12:41 +0100
          Re: $0.03 microcontroller gnuarm.deletethisbit@gmail.com - 2018-10-12 09:11 -0700
            Re: $0.03 microcontroller David Brown <david.brown@hesbynett.no> - 2018-10-13 12:46 +0200
              Re: $0.03 microcontroller gnuarm.deletethisbit@gmail.com - 2018-10-13 05:06 -0700
                Re: $0.03 microcontroller upsidedown@downunder.com - 2018-10-13 18:00 +0300
                Re: $0.03 microcontroller David Brown <david.brown@hesbynett.no> - 2018-10-13 18:27 +0200
                Re: $0.03 microcontroller upsidedown@downunder.com - 2018-10-13 20:50 +0300
                Re: $0.03 microcontroller David Brown <david.brown@hesbynett.no> - 2018-10-14 14:26 +0200
                Re: $0.03 microcontroller gnuarm.deletethisbit@gmail.com - 2018-10-13 18:20 -0700
                Re: $0.03 microcontroller Philipp Klaus Krause <pkk@spth.de> - 2018-10-14 08:53 +0200
                Re: $0.03 microcontroller Philipp Klaus Krause <pkk@spth.de> - 2018-10-14 08:55 +0200
                Re: $0.03 microcontroller David Brown <david.brown@hesbynett.no> - 2018-10-14 14:32 +0200
                Re: $0.03 microcontroller David Brown <david.brown@hesbynett.no> - 2018-10-13 18:21 +0200
                Re: $0.03 microcontroller gnuarm.deletethisbit@gmail.com - 2018-10-13 18:32 -0700
                Re: $0.03 microcontroller Paul Rubin <no.email@nospam.invalid> - 2018-10-13 19:02 -0700
                Re: $0.03 microcontroller David Brown <david.brown@hesbynett.no> - 2018-10-14 14:37 +0200
                Re: $0.03 microcontroller Philipp Klaus Krause <pkk@spth.de> - 2018-10-14 14:59 +0200
                Re: $0.03 microcontroller Paul Rubin <no.email@nospam.invalid> - 2018-10-13 11:06 -0700
            Re: $0.03 microcontroller Niklas Holsti <niklas.holsti@tidorum.invalid> - 2018-10-13 18:31 +0300
              Re: $0.03 microcontroller Niklas Holsti <niklas.holsti@tidorum.invalid> - 2018-10-13 19:46 +0300
                Re: $0.03 microcontroller Niklas Holsti <niklas.holsti@tidorum.invalid> - 2018-10-13 19:59 +0300
                Re: $0.03 microcontroller upsidedown@downunder.com - 2018-10-13 21:31 +0300
                Re: $0.03 microcontroller Niklas Holsti <niklas.holsti@tidorum.invalid> - 2018-10-13 22:19 +0300
                Re: $0.03 microcontroller Philipp Klaus Krause <pkk@spth.de> - 2018-10-13 21:24 +0200
                Re: $0.03 microcontroller Niklas Holsti <niklas.holsti@tidorum.invalid> - 2018-10-13 22:50 +0300
                Re: $0.03 microcontroller David Brown <david.brown@hesbynett.no> - 2018-10-14 14:39 +0200
                Re: $0.03 microcontroller gnuarm.deletethisbit@gmail.com - 2018-10-15 05:11 -0700
              Re: $0.03 microcontroller upsidedown@downunder.com - 2018-10-13 21:03 +0300
              Re: $0.03 microcontroller gnuarm.deletethisbit@gmail.com - 2018-10-13 18:25 -0700
          Re: $0.03 microcontroller Philipp Klaus Krause <pkk@spth.de> - 2018-10-15 14:20 +0200
    Re: $0.03 microcontroller upsidedown@downunder.com - 2018-10-21 16:27 +0300
      Re: $0.03 microcontroller jim.brakefield@ieee.org - 2018-10-21 07:47 -0700
        Re: $0.03 microcontroller gnuarm.deletethisbit@gmail.com - 2018-10-21 08:08 -0700
          Re: $0.03 microcontroller jim.brakefield@ieee.org - 2018-10-21 09:31 -0700
            Re: $0.03 microcontroller gnuarm.deletethisbit@gmail.com - 2018-10-21 10:51 -0700
              Re: $0.03 microcontroller jim.brakefield@ieee.org - 2018-10-21 12:44 -0700
                Re: $0.03 microcontroller Brett <ggtgp@yahoo.com> - 2018-10-22 00:28 +0000
          Re: $0.03 microcontroller David Brown <david.brown@hesbynett.no> - 2018-10-21 21:43 +0200
      Re: $0.03 microcontroller Phil Martel <pomartel@comcast.net> - 2018-10-21 11:03 -0400
      Re: $0.03 microcontroller George Neuner <gneuner2@comcast.net> - 2018-10-21 20:59 -0400
  Re: $0.03 microcontroller Michael Kellett <mk@mkesc.co.uk> - 2018-10-11 14:04 +0100
    Re: $0.03 microcontroller David Brown <david.brown@hesbynett.no> - 2018-10-11 15:56 +0200
      Re: $0.03 microcontroller Michael Kellett <mk@mkesc.co.uk> - 2018-10-13 09:35 +0100
        Re: $0.03 microcontroller Paul Rubin <no.email@nospam.invalid> - 2018-10-13 13:06 -0700
          Re: $0.03 microcontroller Michael Kellett <mk@mkesc.co.uk> - 2018-10-14 11:30 +0100
  Re: $0.03 microcontroller Philipp Klaus Krause <pkk@spth.de> - 2018-10-12 10:18 +0200
    Re: $0.03 microcontroller upsidedown@downunder.com - 2018-10-12 21:39 +0300
      Re: $0.03 microcontroller Philipp Klaus Krause <pkk@spth.de> - 2018-11-08 13:53 +0100
        Re: $0.03 microcontroller Tauno Voipio <tauno.voipio@notused.fi.invalid> - 2018-11-08 15:08 +0200
          Re: $0.03 microcontroller Philipp Klaus Krause <pkk@spth.de> - 2018-11-08 14:34 +0100
        Re: $0.03 microcontroller upsidedown@downunder.com - 2018-11-08 21:52 +0200
          Re: $0.03 microcontroller Philipp Klaus Krause <pkk@spth.de> - 2018-11-08 21:56 +0100
            Re: $0.03 microcontroller upsidedown@downunder.com - 2018-11-09 00:35 +0200
              Re: $0.03 microcontroller Philipp Klaus Krause <pkk@spth.de> - 2018-11-09 09:00 +0100
    Re: $0.03 microcontroller Philipp Klaus Krause <pkk@spth.de> - 2018-10-15 14:19 +0200
  Re: $0.03 microcontroller Tim <cpldcpu+usenet@gmail.com> - 2018-10-14 01:46 +0200
    Re: $0.03 microcontroller Theo <theom+news@chiark.greenend.org.uk> - 2018-10-14 10:55 +0100
      Re: $0.03 microcontroller Philipp Klaus Krause <pkk@spth.de> - 2018-10-24 15:57 +0200
  Re: $0.03 microcontroller Philipp Klaus Krause <pkk@spth.de> - 2018-10-15 14:35 +0200
    Re: $0.03 microcontroller raimond.dragomir@gmail.com - 2018-10-15 06:05 -0700
      Re: $0.03 microcontroller gnuarm.deletethisbit@gmail.com - 2018-10-15 07:19 -0700
        Re: $0.03 microcontroller Paul Rubin <no.email@nospam.invalid> - 2018-10-15 07:26 -0700
          Re: $0.03 microcontroller gnuarm.deletethisbit@gmail.com - 2018-10-15 07:30 -0700

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