Questions of SFCs

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Iconoclast's Avatar (by Gravatar)Iconoclast posted on
March 31, 2008, 8:14 pm
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I've done both PLC & DCS programming over the years, doing both ladder and
function block programming, but I've never been steered to using SFCs for
programming, and, in fact, don't know much about it.

Can anyone tell me what's the usefulness of SFCs? Is SFC used pretty much
for batch programming and/or operations that like machining?




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pnachtwey's Avatar (by Gravatar)pnachtwey posted on
April 1, 2008, 1:05 am
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Re: Questions of SFCs




They are used for machine sequencing.  Basic a SFC is a flow chart
made of steps and transitions.  The steps have actions.  The programs
waits at a step until the transition is true and then the program goes
to the next step. This makes machine sequencing easy and efficient
because instead of scanning the whole program like a PLC, only the
current step and transition are executed.

Note is is possible to have many SFC flow charts executing at the same
time.  This effectively makes the SFC multitasking.

Peter Nachtwey

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F's Avatar (by Gravatar)F posted on
April 7, 2008, 7:30 am
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Re: Questions of SFCs



"They are used for machine sequencing. "
And more, for example S88 Phase logic.
It is important to remember that SFC is just one of many programming methods
that work together. For example an SFC step may enable lower level logic
that is then programmed in ladder, similarly with transitions.
Read more here
http://www.urswriter.com/SFCDraw/sfc_links.html
Francis
www.controldraw.co.uk



They are used for machine sequencing.  Basic a SFC is a flow chart
made of steps and transitions.  The steps have actions.  The programs
waits at a step until the transition is true and then the program goes
to the next step. This makes machine sequencing easy and efficient
because instead of scanning the whole program like a PLC, only the
current step and transition are executed.

Note is is possible to have many SFC flow charts executing at the same
time.  This effectively makes the SFC multitasking.

Peter Nachtwey



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