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Re: Multitasking with Forth processors

From Jan Coombs <jenfhaomndgfwutc@murmic.plus.com>
Newsgroups comp.lang.forth
Subject Re: Multitasking with Forth processors
Date 2017-04-14 12:20 +0100
Organization A noiseless patient Spider
Message-ID <20170414122056.498bab8a@t530.lan> (permalink)
References (8 earlier) <ocile6$7ro$1@dont-email.me> <e11a25dd-5c4c-404e-bbfa-3ec67c7b1d08@googlegroups.com> <2ef60cba-5577-4813-ae93-3946cd4b415b@googlegroups.com> <5ae256e5-1def-4e09-a52a-cd76dc422506@googlegroups.com> <8660iaw5f6.fsf_-_@molnjunk.nocrew.org>

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On Wed, 12 Apr 2017 07:39:25 +0200
Lars Brinkhoff <lars.spam@nocrew.org> wrote:

> A multitasking context switch on a regular processor usually
> involves moving around the stack pointers.
> 
> But in a Forth processor the stacks may be on chip, and the
> stack pointers may not be accessible.  So how would you do a
> context switch in this programming model?

In hardware, for example (from memory):

If your processor is built in a small FPGA with 256x16b RAM
blocks, then your might have 8 tasks with 32 deep stacks, using
one RAM block for each set of 8 stacks. Two RAM blocks in total,
one for data, one for return addresses. 

In this case the lower five bits of stack memory address come
from a task's stack pointer, and the higher three bits from a
task select register, which also selects the current stack
pointer. 

Calling the task switch word PAUSE saves the return address for
the current task on it's currently selected return stack. After
checking the status and priority of other tasks, PAUSE writes a
new value to the task select register if a task switch is
needed. 

When PAUSE exits, the return address comes from the current
task's return stack.  Data belonging to the resumed task is also
on the currently selected data stack. 

This is about the simplest I've seen, there are others. 

Jan Coombs

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Thread

polyForth multitasker question "HAA" <someone@microsoft.com> - 2017-04-08 20:53 +1000
  Re: polyForth multitasker question Andrew Haley <andrew29@littlepinkcloud.invalid> - 2017-04-08 12:29 -0500
    Re: polyForth multitasker question "HAA" <someone@microsoft.com> - 2017-04-10 09:50 +1000
      Re: polyForth multitasker question David Schultz <abuse@127.0.0.1> - 2017-04-09 19:25 -0500
        Re: polyForth multitasker question "HAA" <someone@microsoft.com> - 2017-04-10 10:52 +1000
          Re: polyForth multitasker question Andrew Haley <andrew29@littlepinkcloud.invalid> - 2017-04-10 08:58 -0500
            Re: polyForth multitasker question "HAA" <someone@microsoft.com> - 2017-04-15 10:39 +1000
        Re: polyForth multitasker question "HAA" <someone@microsoft.com> - 2017-04-11 11:12 +1000
          Re: polyForth multitasker question Paul Rubin <no.email@nospam.invalid> - 2017-04-10 18:22 -0700
            Re: polyForth multitasker question "HAA" <someone@microsoft.com> - 2017-04-11 12:17 +1000
          Re: polyForth multitasker question Andrew Haley <andrew29@littlepinkcloud.invalid> - 2017-04-11 03:10 -0500
      Re: polyForth multitasker question "Elizabeth D. Rather" <erather@forth.com> - 2017-04-09 14:37 -1000
        Re: polyForth multitasker question Paul Rubin <no.email@nospam.invalid> - 2017-04-09 18:05 -0700
          Re: polyForth multitasker question "Elizabeth D. Rather" <erather@forth.com> - 2017-04-09 15:50 -1000
          Re: polyForth multitasker question Lars Brinkhoff <lars.spam@nocrew.org> - 2017-04-10 07:47 +0200
        Re: polyForth multitasker question "HAA" <someone@microsoft.com> - 2017-04-10 12:20 +1000
        Re: polyForth multitasker question Alex <alex@rivadpm.com> - 2017-04-10 09:11 +0100
          Re: polyForth multitasker question Andrew Haley <andrew29@littlepinkcloud.invalid> - 2017-04-10 04:20 -0500
            Re: polyForth multitasker question Alex <alex@rivadpm.com> - 2017-04-10 10:53 +0100
              Re: polyForth multitasker question Alex <alex@rivadpm.com> - 2017-04-10 11:24 +0100
              Re: polyForth multitasker question "HAA" <someone@microsoft.com> - 2017-04-11 12:05 +1000
                Re: polyForth multitasker question Alex <alex@rivadpm.com> - 2017-04-11 14:27 +0100
                Re: polyForth multitasker question minforth@arcor.de - 2017-04-11 07:08 -0700
                Re: polyForth multitasker question foxaudioresearch@gmail.com - 2017-04-11 18:06 -0700
                Re: polyForth multitasker question Paul Rubin <no.email@nospam.invalid> - 2017-04-11 18:58 -0700
                Re: polyForth multitasker question foxaudioresearch@gmail.com - 2017-04-12 13:57 -0700
                Re: polyForth multitasker question Paul Rubin <no.email@nospam.invalid> - 2017-04-12 18:02 -0700
                Re: polyForth multitasker question foxaudioresearch@gmail.com - 2017-04-12 19:47 -0700
                Re: polyForth multitasker question Paul Rubin <no.email@nospam.invalid> - 2017-04-12 21:22 -0700
                Re: polyForth multitasker question foxaudioresearch@gmail.com - 2017-04-13 02:57 -0700
                Re: polyForth multitasker question minforth@arcor.de - 2017-04-12 23:17 -0700
                Re: polyForth multitasker question Paul Rubin <no.email@nospam.invalid> - 2017-04-13 00:13 -0700
                Re: polyForth multitasker question "Elizabeth D. Rather" <erather@forth.com> - 2017-04-13 09:43 -1000
                Re: polyForth multitasker question Paul Rubin <no.email@nospam.invalid> - 2017-04-13 19:34 -0700
                Re: polyForth multitasker question "Elizabeth D. Rather" <erather@forth.com> - 2017-04-13 19:57 -1000
                Re: polyForth multitasker question rickman <gnuarm@gmail.com> - 2017-04-14 02:45 -0400
                Re: polyForth multitasker question "Elizabeth D. Rather" <erather@forth.com> - 2017-04-13 21:28 -1000
                Re: polyForth multitasker question anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2017-04-14 07:53 +0000
                Re: polyForth multitasker question Paul Rubin <no.email@nospam.invalid> - 2017-04-14 01:44 -0700
                Re: polyForth multitasker question minforth@arcor.de - 2017-04-14 02:01 -0700
                Re: polyForth multitasker question Paul Rubin <no.email@nospam.invalid> - 2017-04-14 11:28 -0700
                Re: polyForth multitasker question rickman <gnuarm@gmail.com> - 2017-04-14 16:23 -0400
                Re: polyForth multitasker question "Elizabeth D. Rather" <erather@forth.com> - 2017-04-13 22:46 -1000
                Re: polyForth multitasker question anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2017-04-14 11:31 +0000
                Re: polyForth multitasker question Paul Rubin <no.email@nospam.invalid> - 2017-04-14 11:23 -0700
                Re: polyForth multitasker question "Elizabeth D. Rather" <erather@forth.com> - 2017-04-14 10:06 -1000
                Re: polyForth multitasker question Andrew Haley <andrew29@littlepinkcloud.invalid> - 2017-04-14 08:13 -0500
                Re: polyForth multitasker question anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2017-04-14 14:12 +0000
                Re: polyForth multitasker question pahihu <pahihu@gmail.com> - 2017-04-14 09:30 -0700
                Re: polyForth multitasker question anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2017-04-15 08:46 +0000
                Re: polyForth multitasker question pahihu <pahihu@gmail.com> - 2017-04-15 13:07 -0700
                Re: polyForth multitasker question Paul Rubin <no.email@nospam.invalid> - 2017-04-15 17:27 -0700
                Re: polyForth multitasker question foxaudioresearch@gmail.com - 2017-04-15 18:18 -0700
                Re: polyForth multitasker question anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2017-04-17 13:53 +0000
                Re: polyForth multitasker question Andrew Haley <andrew29@littlepinkcloud.invalid> - 2017-04-14 11:34 -0500
                Re: polyForth multitasker question hughaguilar96@gmail.com - 2017-04-14 11:31 -0700
                Re: polyForth multitasker question Julian Fondren <julian.fondren@gmail.com> - 2017-04-14 12:14 -0700
                Re: polyForth multitasker question hughaguilar96@gmail.com - 2017-04-14 12:46 -0700
                Re: polyForth multitasker question hughaguilar96@gmail.com - 2017-04-14 12:48 -0700
                Re: polyForth multitasker question hughaguilar96@gmail.com - 2017-04-14 12:50 -0700
                Re: polyForth multitasker question albert@cherry.spenarnc.xs4all.nl (Albert van der Horst) - 2017-04-15 14:39 +0200
                Re: polyForth multitasker question Julian Fondren <julian.fondren@gmail.com> - 2017-04-15 11:48 -0700
                Re: polyForth multitasker question Alex <alex@rivadpm.com> - 2017-04-14 22:07 +0100
                Re: polyForth multitasker question anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2017-04-15 16:47 +0000
                Re: polyForth multitasker question "Elizabeth D. Rather" <erather@forth.com> - 2017-04-15 11:36 -1000
                Re: polyForth multitasker question foxaudioresearch@gmail.com - 2017-04-15 17:07 -0700
                Re: polyForth multitasker question "Elizabeth D. Rather" <erather@forth.com> - 2017-04-15 14:17 -1000
                Re: polyForth multitasker question hughaguilar96@gmail.com - 2017-04-15 18:27 -0700
                Re: polyForth multitasker question Ron Aaron <rambamist@gmail.com> - 2017-04-16 06:53 +0300
                Re: polyForth multitasker question hughaguilar96@gmail.com - 2017-04-15 22:00 -0700
                Re: polyForth multitasker question Ron Aaron <rambamist@gmail.com> - 2017-04-16 08:59 +0300
                Re: polyForth multitasker question lehs <skydda.barnen@gmail.com> - 2017-04-15 22:19 -0700
                Re: polyForth multitasker question hughaguilar96@gmail.com - 2017-04-15 17:26 -0700
                Re: polyForth multitasker question Andrew Haley <andrew29@littlepinkcloud.invalid> - 2017-04-16 09:10 -0500
                Re: polyForth multitasker question "Elizabeth D. Rather" <erather@forth.com> - 2017-04-16 09:13 -1000
                Re: polyForth multitasker question anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2017-04-16 16:28 +0000
                Re: polyForth multitasker question "Elizabeth D. Rather" <erather@forth.com> - 2017-04-16 09:27 -1000
                Re: polyForth multitasker question Paul Rubin <no.email@nospam.invalid> - 2017-04-16 14:45 -0700
                Re: polyForth multitasker question "Elizabeth D. Rather" <erather@forth.com> - 2017-04-16 17:50 -1000
                Re: polyForth multitasker question anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2017-04-17 12:13 +0000
                Re: polyForth multitasker question Paul Rubin <no.email@nospam.invalid> - 2017-04-17 13:27 -0700
                Re: polyForth multitasker question Andrew Haley <andrew29@littlepinkcloud.invalid> - 2017-04-18 03:49 -0500
                Re: polyForth multitasker question Alex <alex@rivadpm.com> - 2017-04-18 13:47 +0100
                Re: polyForth multitasker question Andrew Haley <andrew29@littlepinkcloud.invalid> - 2017-04-18 14:30 -0500
                Re: polyForth multitasker question hughaguilar96@gmail.com - 2017-04-16 20:58 -0700
                Re: polyForth multitasker question "HAA" <someone@microsoft.com> - 2017-04-18 11:47 +1000
                Re: polyForth multitasker question Paul Rubin <no.email@nospam.invalid> - 2017-04-17 19:19 -0700
                Re: polyForth multitasker question Andrew Haley <andrew29@littlepinkcloud.invalid> - 2017-04-18 04:34 -0500
                Re: polyForth multitasker question Paul Rubin <no.email@nospam.invalid> - 2017-04-19 02:00 -0700
                Re: polyForth multitasker question "HAA" <someone@microsoft.com> - 2017-04-19 18:10 +1000
                Re: polyForth multitasker question Paul Rubin <no.email@nospam.invalid> - 2017-04-19 01:41 -0700
                Re: polyForth multitasker question "HAA" <someone@microsoft.com> - 2017-04-19 21:38 +1000
                Re: polyForth multitasker question Lars Brinkhoff <lars.spam@nocrew.org> - 2017-04-19 10:56 +0200
                Re: polyForth multitasker question Andrew Haley <andrew29@littlepinkcloud.invalid> - 2017-04-19 07:22 -0500
                Re: polyForth multitasker question hughaguilar96@gmail.com - 2017-04-17 20:10 -0700
                Re: polyForth multitasker question stephen@mpeforth.com (Stephen Pelc) - 2017-04-18 09:35 +0000
                Re: polyForth multitasker question hughaguilar96@gmail.com - 2017-04-18 08:01 -0700
                Re: polyForth multitasker question Julian Fondren <julian.fondren@gmail.com> - 2017-04-18 09:03 -0700
                Re: polyForth multitasker question Cecil Bayona <cbayona@cbayona.com> - 2017-04-18 11:07 -0500
                Re: polyForth multitasker question Cecil Bayona <cbayona@cbayona.com> - 2017-04-18 10:59 -0500
                Re: polyForth multitasker question "HAA" <someone@microsoft.com> - 2017-04-19 19:13 +1000
                Re: polyForth multitasker question Paul Rubin <no.email@nospam.invalid> - 2017-04-15 17:36 -0700
                Re: polyForth multitasker question anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2017-04-16 16:27 +0000
                Re: polyForth multitasker question Andrew Haley <andrew29@littlepinkcloud.invalid> - 2017-04-16 04:32 -0500
                Re: polyForth multitasker question "Elizabeth D. Rather" <erather@forth.com> - 2017-04-14 10:15 -1000
                Re: polyForth multitasker question albert@cherry.spenarnc.xs4all.nl (Albert van der Horst) - 2017-04-15 13:07 +0200
                Re: polyForth multitasker question anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2017-04-17 15:13 +0000
                Re: polyForth multitasker question Paul Rubin <no.email@nospam.invalid> - 2017-04-14 01:36 -0700
                Re: polyForth multitasker question "Elizabeth D. Rather" <erather@forth.com> - 2017-04-13 22:48 -1000
                Re: polyForth multitasker question rickman <gnuarm@gmail.com> - 2017-04-14 16:36 -0400
                Re: polyForth multitasker question Paul Rubin <no.email@nospam.invalid> - 2017-04-14 14:55 -0700
                Re: polyForth multitasker question hughaguilar96@gmail.com - 2017-04-14 15:27 -0700
                Re: polyForth multitasker question Alex <alex@rivadpm.com> - 2017-04-14 23:45 +0100
                Re: polyForth multitasker question hughaguilar96@gmail.com - 2017-04-16 21:13 -0700
                Re: polyForth multitasker question Alex <alex@rivadpm.com> - 2017-04-17 16:57 +0100
                Re: polyForth multitasker question hughaguilar96@gmail.com - 2017-04-17 20:08 -0700
                Re: polyForth multitasker question rickman <gnuarm@gmail.com> - 2017-04-14 20:29 -0400
                Re: polyForth multitasker question "Elizabeth D. Rather" <erather@forth.com> - 2017-04-14 15:34 -1000
                Re: polyForth multitasker question Paul Rubin <no.email@nospam.invalid> - 2017-04-14 19:43 -0700
                Re: polyForth multitasker question rickman <gnuarm@gmail.com> - 2017-04-14 23:03 -0400
                Re: polyForth multitasker question Paul Rubin <no.email@nospam.invalid> - 2017-04-14 23:50 -0700
                Re: polyForth multitasker question rickman <gnuarm@gmail.com> - 2017-04-15 03:55 -0400
                Re: polyForth multitasker question Paul Rubin <no.email@nospam.invalid> - 2017-04-15 01:38 -0700
                Re: polyForth multitasker question rickman <gnuarm@gmail.com> - 2017-04-15 11:50 -0400
                Re: polyForth multitasker question john <anon@example.com> - 2017-04-15 12:03 +0100
                Re: polyForth multitasker question anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2017-04-15 12:41 +0000
                Re: polyForth multitasker question rickman <gnuarm@gmail.com> - 2017-04-15 12:14 -0400
                Re: polyForth multitasker question Paul Rubin <no.email@nospam.invalid> - 2017-04-15 17:32 -0700
                Re: polyForth multitasker question rickman <gnuarm@gmail.com> - 2017-04-15 20:41 -0400
                Re: polyForth multitasker question anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2017-04-17 14:57 +0000
                Re: polyForth multitasker question hughaguilar96@gmail.com - 2017-04-14 20:45 -0700
                Re: polyForth multitasker question rickman <gnuarm@gmail.com> - 2017-04-14 23:56 -0400
                Re: polyForth multitasker question albert@cherry.spenarnc.xs4all.nl (Albert van der Horst) - 2017-04-15 14:32 +0200
                Re: polyForth multitasker question rickman <gnuarm@gmail.com> - 2017-04-15 12:05 -0400
                Re: polyForth multitasker question Andrew Haley <andrew29@littlepinkcloud.invalid> - 2017-04-15 04:10 -0500
                Re: polyForth multitasker question foxaudioresearch@gmail.com - 2017-04-13 03:19 -0700
                Re: polyForth multitasker question Alex <alex@rivadpm.com> - 2017-04-13 15:46 +0100
                Re: polyForth multitasker question foxaudioresearch@gmail.com - 2017-04-14 11:37 -0700
                Re: polyForth multitasker question "Elizabeth D. Rather" <erather@forth.com> - 2017-04-13 09:48 -1000
                Re: polyForth multitasker question Andrew Haley <andrew29@littlepinkcloud.invalid> - 2017-04-13 05:37 -0500
                Re: polyForth multitasker question minforth@arcor.de - 2017-04-11 22:12 -0700
                Multitasking with Forth processors Lars Brinkhoff <lars.spam@nocrew.org> - 2017-04-12 07:39 +0200
                Re: Multitasking with Forth processors Paul Rubin <no.email@nospam.invalid> - 2017-04-11 22:58 -0700
                Re: Multitasking with Forth processors rickman <gnuarm@gmail.com> - 2017-04-12 03:00 -0400
                Re: Multitasking with Forth processors albert@cherry.spenarnc.xs4all.nl (Albert van der Horst) - 2017-04-12 12:18 +0200
                Re: Multitasking with Forth processors rickman <gnuarm@gmail.com> - 2017-04-12 17:11 -0400
                Re: Multitasking with Forth processors foxaudioresearch@gmail.com - 2017-04-12 13:50 -0700
                Re: Multitasking with Forth processors "Elizabeth D. Rather" <erather@forth.com> - 2017-04-12 13:30 -1000
                Re: Multitasking with Forth processors Jan Coombs <jenfhaomndgfwutc@murmic.plus.com> - 2017-04-14 12:20 +0100
                Re: Multitasking with Forth processors rickman <gnuarm@gmail.com> - 2017-04-14 16:47 -0400
            Re: polyForth multitasker question "Elizabeth D. Rather" <erather@forth.com> - 2017-04-10 07:42 -1000

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