Wouter van Ooijen wrote:

> > FSM is one of the few programming techniques that really
> > should be implemented in a graphical programming language.
>
> I disagree:
>
> 1. A non-trivial state machine contains, beside the state-stuff itself,
> a lot of plain and (not so) simple code. I don't see how anything but a
> HLL (for asm lovers: assembler) would be usefull for that part.

I agree with you on this. I did not mean that every aspect of the programming
proceadure should be done using diagrams. Yes write A=B+2 where it is
appropriote but use diagrams to program the relationships between the states and
events. The event transition and monitor functions can be written in anything
you like.

>
> 2. A non-trivial state machine contains far too many states, events and
> transitions to be reasonably represented in a graphical way. Think
> 10..20 states, same number of events.

I disagree here. A large system consisting of hundreds of states and thousands
of events can be much more easily managed using an appropriate tool. Think of a
large silicon chip with huge numbers of features. scroll around, zoom in. Same
with a huge state diagram. Also with the right tools you can build small state
machines, test them then use them as components in larger state machines.

I have worked on systems that have had tens of states and hundreds of events
which although they were described as state machines - were anything but. Large
state machines are very hard to verify and often people take short cuts because
they need a quick fix. These systems degenerate into a collection of hacks and
the documentation becomes almost useless. If you use the right tools you don't
have to resort to short cuts, you can add a few more states and events in the
time it takes you to draw a few boxes, add a couple of lines and type in the
names.

Have a look at
http://www.xcprod.com/titan/ZMECH-DOC/generate/state-machine/block-indx.html
34 states and 88 events. The diagram shows a multimaster I2C system. It would
look better on the screen if you shrank it down and scrolled and zoomed but that
defeats the objective of presenting it as a html image with anotated hot spots.

Regards
Sergio Masci

http://www.xcprod.com/titan/XCSB - optimising structured PIC BASIC compiler

--
http://www.piclist.com hint: The PICList is archived three different
ways.  See http://www.piclist.com/#archives for details.