allscott said:
So why again are we using ethernet for control? someone edumacate me please?
Uhhh... I can't.
I suppose, it is because as a networking standard, Ethernet is really The King (sorry Elvis).
From an actual 'Control' Standpoint, I despise the very thought of using Ethernet to control remote devices.
I accept (and even, lovingly use) Ethernet to talk between HMI's and process devices (well, PLC's), but I insist on having physical 'Line Start', 'Line Stop', 'Line Jog', 'Line Thread', 'Emergency Stop', and 'Emergency Stop Reset' buttons as a minimum.
I don't really care what managed N-TRON, or Phoenix, or Cisco switch people are using, unless they fully and completely understand the Ethernet (physical layer) protocols, they are asking for trouble. Ethernet is fantastic for setting up machine parameters, and 'tweaking' things, but it is still a long way away from being my choice protocol for actually controlling devices in real time.
Why?
How many 'Ethernet Only' advocets out there have ever heard of 'STP' ?
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I was going to describe what STP is, and what it does, and why it is absolutely essential if you rely on Ethernet for your systems control, but I'll leave that to the reader to research.
Let's see who answers correctly first