Ethernet Debates

Nothing like a good debate to get the adrenaline flowing now that I’m back in the office.  Nick Belardes (ProSoft) and Eric Murphy (MatrikonOPC) have a bit of a conversation flowing covering Ethernet, OPC, and Modbus.  I like to think of Modbus as a stand-in for fieldbuses in general.

Seems like some folks think that OPC and fieldbuses (or open Ethernet protocols like PROFINET) are competing technologies.  Eric points out that they’re complementary.  I feel compelled to expand on that a bit.  A couple weeks ago I sat down with Tom Burke, OPC’s head honcho, to explore that topic in depth.  Specifically we were comparing PROFINET and OPC (starting with DA and moving to UA).  Actually, comparing is the wrong word; we were mostly contrasting the two.

PROFINET’s domain is control where speeds from microseconds to 10’s of milliseconds are needed.  OPC’s domain is upward communication to HMIs, historians, MES, etc. where speeds in fractions of a second to multiple seconds are the norm.  PROFINET can connect disparate fieldbuses (including Modbus) for control purposes.  OPC can gather data for display purposes from various fieldbuses.  There are OPC Servers for PROFINET so that control data can be sent to HMIs etc.  See, clearly complementary.

Oh, wait a minute – haven’t I bragged about PROFINET connecting to MES and now I just said OPC is designed to connect to MES (among other things).  Is there some overlap there?  Maybe some, but as I understand it, OPC provides an infrastructure that can be used to communicate Asset Management information (for example) while PROFINET provides both an infrastructure and a structure for Asset Management information.  We’ll have to see how this plays out in the market place.

I’d like to say that it’s great being back in the office.  Having my first first-hand experience with Hawaii, I have to say that there’s no debate, it’s one beautiful state!  Driving up the west coast of the big island, I observed that it was just like driving through northern Arizona… except for the whales spouting and breeching off the coast.  More specifically, the terrain and vegetation were just like Arizona.  Arizona does not actually have a coast… yet.