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Old October 10th, 2018, 11:49 AM   #1
Prayder
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Communication Protocol

I have no doubt the question I am about to ask is dumb, but I don't know so I'm going to ask:

How can you tell the difference in communication protocols like Ethernet IP, Profinet, profibus, etc.

How can you tell which actual communication protocol you are using?
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Old October 10th, 2018, 12:27 PM   #2
geniusintraining
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Quote:
Originally Posted by Prayder View Post
I have no doubt the question I am about to ask is dumb, but I don't know so I'm going to ask:

How can you tell the difference in communication protocols like Ethernet IP, Profinet, profibus, etc.

How can you tell which actual communication protocol you are using?
I think you need to have an idea of the equipment that your working with and go back to the manuals with the equipment, I sold some trainers to a instructor that was teaching protocol and what it looked like 'behind the scenes' but never got to see it for myself, I did see one thread that Bernie hooked up a scope and was reading the ASCII signal but it was several years back, I think you maybe able to see a difference using some sort of port sniffer and you maybe able to tell the difference

I also dont think its a dumb question...
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Old October 10th, 2018, 12:29 PM   #3
harryting
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It's like anything else, you look up the documentation and dig through the program.

There are also clues by looking at the actual install to see which hardware is used.
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Old October 10th, 2018, 02:44 PM   #4
Mad_Poet
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As they said, look in the documentation.

Also, look for the part number of the module handling the communications.
Then look it up on the internet. Usually the part number will lead one to a
description of the module which in turn will depict what sort of protocol it
is using.
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Old October 10th, 2018, 03:28 PM   #5
Tom Jenkins
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There are limited bits of info you can get without documentation. The documentation is needed for final verification of everything.

First, Ethernet is not a protocol, it is a transmission method. It identifies a uniform data packet structure. Any Ethernet device can talk to any other, provided the transmission rate and transmission medium are the same. For example, both must be 10base-T on fiber, etc. If you have CAT 5E cable you probably have Ethernet.

However, being able to send data packets doesn't mean that the devices can understand each other. The protocol embedded in the data packet must match for that to happen. For example, both devices must be using Profinet or Modbus/TCP for data exchange t work.

If you have all devices on a network from one manufacturer odds are you will find one of their protocols in use. For example, if you have all Siemens on the network you will probably have Profinet of Profibus.
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Old October 10th, 2018, 04:16 PM   #6
lfe
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There is not a fixed rule, some protocols define almost everything in their documentation, including the type of cable and the connectors to be used but others work on a standard physical medium such as Ethernet or a standard serial communication and then this part is not defined.

Some are only used for a specific application such as remote input/output but others include several versions for different uses such as Ethernet/IP.

As others have already said you have to read the documentation.
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Old October 10th, 2018, 06:23 PM   #7
danw
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Quote:
Originally Posted by Tom Jenkins View Post
If you have CAT 5E cable you probably have Ethernet.
RJ-45 connectors (standard for CAT cable) are used for all sorts of serial communications that is/are not Ethernet.

One has to be careful about what hardware is behind the RJ-45 connector. Back to the documentation.
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Old October 11th, 2018, 03:48 AM   #8
cardosocea
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Quote:
Originally Posted by Prayder View Post
I have no doubt the question I am about to ask is dumb, but I don't know so I'm going to ask:

How can you tell the difference in communication protocols like Ethernet IP, Profinet, profibus, etc.

How can you tell which actual communication protocol you are using?
Partly by knowing what the physical protocol or media they are based on... and partly by whatever brand that particular protocol is associated with.
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Old October 11th, 2018, 07:23 AM   #9
geniusintraining
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Quote:
Originally Posted by danw View Post
RJ-45 connectors (standard for CAT cable) are used for all sorts of serial communications that is/are not Ethernet.

One has to be careful about what hardware is behind the RJ-45 connector. Back to the documentation.
Very true... I get a few phone calls a month people asking why their Ethernet ports are not working on the SLC's and not 5/05's they are DH485 with 24VDC power on them.
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Old October 11th, 2018, 10:35 AM   #10
Fred_Loveless
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Not a dumb or stupid question at all. We routinely get calls from customer asking us what driver they need to use to talk to a piece of hardware. With standard PLC's that is easy. For the smaller manufacturers you have to to to the documentation and event then it is some times hard.

Ethernet IP is a general protocol that typically encapsulates other protocols For example the CIP protocol that is uses for ControlLogix devices is protocol that is transmitted as a payload in an EIP packet. I believe Profinet is similar.

In some cases I have customers do a wireshark or serial port capture so that I can see what is actually going out on the wire. Sometimes we get lucky and can identify the protocol that way. However the documentation is the best way to go. You should be able to get the information from the device specification.
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Old October 13th, 2018, 05:54 AM   #11
rdrast
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Quote:
Originally Posted by danw View Post
RJ-45 connectors (standard for CAT cable) are used for all sorts of serial communications that is/are not Ethernet.

One has to be careful about what hardware is behind the RJ-45 connector. Back to the documentation.

8P8C connector is what you are looking at.

A True "RJ-45" "Registered Jack 45" is actually a completely different connector. RJ types are keyed, 8P8C Ethernet is not.
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