Re: EMC Block Diagram

["alex" <telecomt-at-tht.net>]

I must admit, DOS is only good for running one loop. If its more the one -
forget it,
RT Linux would be an answer.
I confess, I really don't understand how EMC works and was planning to
get into it in 1 month or so. So all the work you will do in clarifying it,
John, will be
like a blessing.
Regards, Alex
----- Original Message -----
From: <jmkasunich-at-ra.rockwell.com>
To: Multiple recipients of list <emc-at-nist.gov>
Sent: Thursday, April 03, 2003 5:22 PM
Subject: EMC Block Diagram


>
>
>
> All these recent discussions about running EMC on remote
> computers, running DOS computers to offload the realtime
> parts of EMC, and so on have pointed out a serious problem:
>
> We really need a block diagram that shows how EMC works.
>
> The only ones I have seen are in the handbook, and look
> like this:
>
> http://linuxcnc.org/handbook/intro/images/whatstep1.gif
> http://linuxcnc.org/handbook/intro/images/whatpc.gif
>
> "whatpc.gif" is nowhere near detailed enough, especially
> in the realtime area.  The single block labeled "Motion
> Control Routines" is actually at least two, (maybe three)
> independent real-time threads, running at different
> speeds and doing different tasks (Motion planning, servo
> loops, and step generation).
>
> Some of the ideas mentioned lately seem to reflect a lack
> of understanding of how the program works, what parts of
> it are fine as they are, and what parts could benefit from
> hardware assistance.  I'll be the first to admit that
> I don't know enough myself about the inner workings of EMC.
> I know that step generation is really fast hard realtime.
> Servo loops are fairly fast hard realtime.  Motion planning
> is also hard realtime, or at least I think it is.  Beyond
> that, I don't know which functions are implemented in real
> time tasks, and which ones are implemented in normal Linux
> tasks, nor do I understand the inter-task communications,
> except to know that NML plays a big role.
>
> I'll volunteer to make the drawing.  I use EasyCad, and
> can post DWG, DXF, postscript, and bitmap  (gif or png)
> files.  For now, I'll post on my website.  Hopefully
> when the drawing is finished, it can go on linuxcnc.org
> or in the handbook.
>
> I think I have a decent understanding of the real-time
> stuff, but I understand nothing about the GUI, NML, and
> higher level code.  I also don't understand the actual
> details of the real-time code - which modules perform
> which tasks for instance.  I'll make a first pass
> this weekend, then post it.  I need someone, or several
> someones, to volunteer to correct my mistakes and fill
> in details.
>
> I'd like to make real progress on this before NAMES.
> Having a good block diagram to point at might make
> conversations easier.  NAMES will also be a great
> opportunity to make corrections and improvements to
> the drawing.
>
>
> John Kasunich
>
>
>
>