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Re: Is it possible to have the following words (RP@ RP! SP@ SP!) on hardware data and return stack

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On Tue, 17 Mar 2015 02:40:14 -0700 (PDT)
mfanyikazi@gmail.com wrote:
 
> James Bowman's J1 FPGA 

The j1 can return the stack pointers, but not set them, so you will 
need to extend it to do multi-tasking.  
 
I'd do the task switch in hardware like NC4016 (in old app note?):  

Add two new hardware registers, and map them into j1 I/O space:
  task-selector - to select a task, must initialise to zero. 
  last-task - last task to run, must initialise to zero. 

Make multiple copies of DSP and RSP, only an extra 10 latches per task, 
plus mux code to select active pair using task-selector

Use larger memories for D and R stacks, and drive most significant
address bits with task-selector


: pause ( ? -- ? ) (R ? -- ? )  \ simplest - runs tasks 0 to last-task
         \ call to pause has pushed curr task return address
    dup  \ push TOS register onto stack 
    \ wrap task selector, even if out of range
    task-selector @ 1+  dup last-task @ >=  if  drop 0  then  
    task-selector !  \ switch stacks, (or not if single tasking) 
    noop  \ may need delay for h/w here
    drop  \ refill task TOS register 
    ;     \ exit to address retrieved from R stack


: my-task ( -- )  \ code for task
    begin  pause ( do something )  again ;

: setup-task ( c-addr task# -- )  \ hookup task
    task-selector !  execute pause  ;

' my-task  1  setup-task  \ setup task 1

1 last-task !  \ allow task 1 to run
0 last-task !  \ single task only


Warning: All from memory, deliberately crude and obvious, more 
could be moved into hardware, and refined, ... 

Would you like some help to test this? 

Jan Coombs
-- 
email valid, else fix dots and hyphen
jan4clf2014@murrayhyphenmicroftdotcodotuk

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Is it possible to have the following words (RP@ RP! SP@ SP!) on hardware data and return stack mfanyikazi@gmail.com - 2015-03-16 09:30 -0700
  Re: Is it possible to have the following words (RP@ RP! SP@ SP!) on hardware data and return stack jenfhaomndgfwutc@murmic.plus.com - 2015-03-16 17:13 +0000
    Re: Is it possible to have the following words (RP@ RP! SP@ SP!) on hardware data and return stack mfanyikazi@gmail.com - 2015-03-17 02:40 -0700
      Re: Is it possible to have the following words (RP@ RP! SP@ SP!) on hardware data and return stack Jan Coombs <Jan-54 <jenfhaomndgfwutc@murmic.plus.com>> - 2015-03-18 01:53 +0000
        Re: Is it possible to have the following words (RP@ RP! SP@ SP!) on hardware data and return stack rickman <gnuarm@gmail.com> - 2015-03-17 23:21 -0400
  Re: Is it possible to have the following words (RP@ RP! SP@ SP!) on hardware data and return stack albert@spenarnc.xs4all.nl (Albert van der Horst) - 2015-03-16 22:24 +0000
    Re: Is it possible to have the following words (RP@ RP! SP@ SP!) on hardware data and return stack rickman <gnuarm@gmail.com> - 2015-03-17 14:01 -0400
      Re: Is it possible to have the following words (RP@ RP! SP@ SP!) on hardware data and return stack JUERGEN <epldfpga@aol.com> - 2015-03-17 11:59 -0700
        Re: Is it possible to have the following words (RP@ RP! SP@ SP!) on hardware data and return stack rickman <gnuarm@gmail.com> - 2015-03-17 16:28 -0400
        Re: Is it possible to have the following words (RP@ RP! SP@ SP!) on hardware data and return stack anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2015-03-18 15:30 +0000
          Re: Is it possible to have the following words (RP@ RP! SP@ SP!) on hardware data and return stack Bernd Paysan <bernd.paysan@gmx.de> - 2015-03-18 22:12 +0100
  Re: Is it possible to have the following words (RP@ RP! SP@ SP!) on hardware data and return stack "Rod Pemberton" <buzz@notnotnontnooatno.cmm> - 2015-03-16 18:57 -0400
    Re: Is it possible to have the following words (RP@ RP! SP@ SP!) on hardware data and return stack mfanyikazi@gmail.com - 2015-03-17 02:52 -0700
      Re: Is it possible to have the following words (RP@ RP! SP@ SP!) on hardware data and return stack "Rod Pemberton" <buzz@notnotnontnooatno.cmm> - 2015-03-17 18:03 -0400
      Re: Is it possible to have the following words (RP@ RP! SP@ SP!) on hardware data and return stack anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2015-03-18 14:39 +0000
  Re: Is it possible to have the following words (RP@ RP! SP@ SP!) on hardware data and return stack mfanyikazi@gmail.com - 2015-03-17 02:58 -0700
  Re: Is it possible to have the following words (RP@ RP! SP@ SP!) on hardware data and return stack anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2015-03-17 16:48 +0000
  Re: Is it possible to have the following words (RP@ RP! SP@ SP!) on hardware data and return stack Lars Brinkhoff <lars.spam@nocrew.org> - 2015-03-18 12:16 +0100
    Re: Is it possible to have the following words (RP@ RP! SP@ SP!) on hardware data and return stack Lars Brinkhoff <lars.spam@nocrew.org> - 2015-03-18 12:43 +0100

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