Re: Text on FSM

From	Bill Davy <Bill@XchelSys.co.uk>
Newsgroups	comp.arch.embedded
Subject	Re: Text on FSM
Date	2023-03-10 08:37 +0000
Message-ID	<k708ipFq7ktU1@mid.individual.net> (permalink)
References	<ba8e4635-0eb1-4a92-99a7-e6bf7ba67e14n@googlegroups.com> <tue3k0$1mrq0$2@dont-email.me>

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On 10/03/2023 02:11, Don Y wrote:
> On 3/9/2023 3:17 PM, jmariano wrote:
>> Hello Does anyone know of a nice text on finite state machines and their
>> software implementation on embedded systems?
> 
> Implementations can vary widely.  Do you want to present (current state,
> inputs) to a machine and have (next_state, outputs) emitted "immediately"?
> Or, is the processing time not critical (e.g., UI's tend to be this type)
> 
> Do you want to limit the machine to the "classic" design?  Or, add
> extensions (e.g., support the notion of "previous_state", "subroutines",
> etc.)?
> 
>> I'm looking for some theoretical background and design methodology. A few
>> examples of "C" implementation would be a nice but not really needed. I'm
>> not looking for a recipe or code but for a more formal explanation on the
>> workings of FSM. Thanks jmariano
> 
> In the degenerate case, you build a matrix that is accessed by 
> [state][inputs]
> and delivers (next_state, outputs).  But, it's obvious that the size of
> this structure grows quickly with number of states and inputs.  In 
> practice,
> often a state may have only a few significant inputs that govern the choice
> of next state so the matrix contains lots of redundant entries.
> 
> You can unfold the matrix into a series of switch/case statements -- but,
> I've found that makes it hard to sort out what's really happening (the
> beauty of a state machine is that it is concise).
> 
> I prefer representations like:
> 
>      Case  IDLE
> On    <digit>        GoTo    ACCEPTING    Executing    GobbleDigit()
> On    <clear>        GoTo    ISSUE_PROMPT    Executing    ClearValue()
> On    <enter>        GoTo    TEST_VALUE    Executing    CheckLimits()
> ..
> 
> Note that there are only 3 items encoded on each line:
> - the input being examined
> - the name of the intended next_state
> - the action to be performed *in* the transition
> As such, this can be encoded in as few as 3 bytes (depending on how
> many states, inputs, and actions you need to support)
> 
> But, the big advantage is it's concise -- no extra syntactic sugar
> to clutter up the page (cuz you want to express the machine in
> as little space as possible as it gets harder to chase layers of
> case/switch statements with interspersed *actions*)
> 
> [There are also UML techniques for their representation and tools that will
> parse such descriptions and build the code for you]
> 
> In school, Hill & Peterson was our reference (_Intro to Switching Theory 
> and
> Logical Design_) but you don't need much "text" to understand the concepts
> (assuming you already understand logic).
> 
> OTOH, it's worth learning about minimization techniques -- esp if your
> approach to the machine's design is /ad hoc/ (ripe for hidden 
> optimizations).
> 

I went to a course of lectures on (and by) Harel state-charts.

Here is one for text: https://github.com/cepsdev/machines4ceps

There is also
https://www.codeproject.com/Articles/11398/A-Lightweight-Implementation-of-UML-Statecharts-in

Thread

Text on FSM jmariano <jmariano65@gmail.com> - 2023-03-09 14:17 -0800
  Re: Text on FSM Rick C <gnuarm.deletethisbit@gmail.com> - 2023-03-09 16:52 -0800
  Re: Text on FSM Don Y <blockedofcourse@foo.invalid> - 2023-03-09 19:11 -0700
    Re: Text on FSM Bill Davy <Bill@XchelSys.co.uk> - 2023-03-10 08:37 +0000
      Re: Text on FSM Don Y <blockedofcourse@foo.invalid> - 2023-03-10 03:50 -0700
  Re: Text on FSM pozz <pozzugno@gmail.com> - 2023-03-10 09:54 +0100
    Re: Text on FSM Don Y <blockedofcourse@foo.invalid> - 2023-03-10 04:17 -0700
    Re: Text on FSM Robert Roland <fake@ddress.no> - 2023-03-10 12:48 +0100
      Re: Text on FSM Rick C <gnuarm.deletethisbit@gmail.com> - 2023-03-10 07:20 -0800
        Re: Text on FSM pozz <pozzugno@gmail.com> - 2023-03-13 16:35 +0100
          Re: Text on FSM StateMachineCOM <statemachineguru@gmail.com> - 2023-03-13 08:55 -0700
            Re: Text on FSM pozz <pozzugno@gmail.com> - 2023-03-14 15:44 +0100
          Re: Text on FSM Don Y <blockedofcourse@foo.invalid> - 2023-03-13 09:29 -0700
            Re: Text on FSM pozz <pozzugno@gmail.com> - 2023-03-14 15:54 +0100
              Re: Text on FSM Don Y <blockedofcourse@foo.invalid> - 2023-03-14 08:39 -0700
              Re: Text on FSM Niklas Holsti <niklas.holsti@tidorum.invalid> - 2023-03-14 18:49 +0200
      Re: Text on FSM Don Y <blockedofcourse@foo.invalid> - 2023-03-10 09:39 -0700
        Re: Text on FSM Don Y <blockedofcourse@foo.invalid> - 2023-03-10 10:02 -0700
        Re: Text on FSM Ed Prochak <edprochak@gmail.com> - 2023-03-10 10:10 -0800
          Re: Text on FSM Don Y <blockedofcourse@foo.invalid> - 2023-03-10 12:10 -0700
            Re: Text on FSM Don Y <blockedofcourse@foo.invalid> - 2023-03-10 12:49 -0700
            Re: Text on FSM Ed Prochak <edprochak@gmail.com> - 2023-03-10 14:02 -0800
              Re: Text on FSM Don Y <blockedofcourse@foo.invalid> - 2023-03-11 06:01 -0700
                Re: Text on FSM Don Y <blockedofcourse@foo.invalid> - 2023-03-11 06:17 -0700
  Re: Text on FSM StateMachineCOM <statemachineguru@gmail.com> - 2023-03-10 07:54 -0800
  Re: Text on FSM jmariano <jmariano65@gmail.com> - 2023-03-10 09:51 -0800
    Re: Text on FSM Rick C <gnuarm.deletethisbit@gmail.com> - 2023-03-10 11:27 -0800
    Re: Text on FSM Don Y <blockedofcourse@foo.invalid> - 2023-03-10 12:46 -0700
    Re: Text on FSM Ed Prochak <edprochak@gmail.com> - 2023-03-10 13:11 -0800
    Re: Text on FSM Gerhard Hoffmann <dk4xp@arcor.de> - 2023-03-13 21:20 +0100
      Re: Text on FSM Don Y <blockedofcourse@foo.invalid> - 2023-03-13 15:41 -0700
        Re: Text on FSM George Neuner <gneuner2@comcast.net> - 2023-03-13 23:07 -0400
          Re: Text on FSM Don Y <blockedofcourse@foo.invalid> - 2023-03-13 22:59 -0700
            Re: Text on FSM George Neuner <gneuner2@comcast.net> - 2023-03-14 21:29 -0400
              Re: Text on FSM Don Y <blockedofcourse@foo.invalid> - 2023-03-14 19:40 -0700
                Re: Text on FSM George Neuner <gneuner2@comcast.net> - 2023-03-22 16:37 -0400
                Re: Text on FSM Don Y <blockedofcourse@foo.invalid> - 2023-03-22 18:15 -0700
                Re: Text on FSM George Neuner <gneuner2@comcast.net> - 2023-03-26 00:45 -0400
                Re: Text on FSM Don Y <blockedofcourse@foo.invalid> - 2023-03-26 03:35 -0700
                Re: Text on FSM George Neuner <gneuner2@comcast.net> - 2023-03-27 02:32 -0400
                Re: Text on FSM Don Y <blockedofcourse@foo.invalid> - 2023-03-27 01:16 -0700
                Re: Text on FSM George Neuner <gneuner2@comcast.net> - 2023-03-28 15:25 -0400
                Re: Text on FSM Don Y <blockedofcourse@foo.invalid> - 2023-03-28 16:56 -0700
                Re: Text on FSM Clifford Heath <no.spam@please.net> - 2023-03-27 16:18 +1100
                Re: Text on FSM George Neuner <gneuner2@comcast.net> - 2023-03-28 11:17 -0400
                Re: Text on FSM Clifford Heath <no.spam@please.net> - 2023-03-29 09:00 +1100
                Re: Text on FSM George Neuner <gneuner2@comcast.net> - 2023-03-28 21:27 -0400
                Re: Text on FSM Clifford Heath <no.spam@please.net> - 2023-03-30 08:33 +1100
                Re: Text on FSM Richard Damon <Richard@Damon-Family.org> - 2023-03-28 21:31 -0400
  Re: Text on FSM George Neuner <gneuner2@comcast.net> - 2023-03-10 16:49 -0500

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