adccommunitymod (AutomationDirect) asked a question.
Created Date: April 19,2011
Created By: clintonp
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I'm looking for a push in the right direction for a couple of VERY basic questions. Using a DL06 with an H0-ECOM100, I have to interrogate a timeserver on the network. I'll have to send it a request, and listen for the response (an NTP time stamp). I don't know where to begin to do the actual i/o. What I have so far is the hardware, and the IP address of the timeserver. Can someone point me toward documentation of the steps involved in sending the request and picking up the response? I have not read every word of Chapter 4 of the ECOM manual yet ( RLL Programming for Communications ), but it looks like that won't help -- it seems to focus on peer-to-peer PLC communication. Paul in WI
Created Date: April 19,2011
Created by: franji1
The ECOM100 only speaks certain protocols, and SNTP is not one of them. Nor can you "roll your own " TCP or UDP protocol.
We are looking to support the Simple Network Time Protocol client in a future PLC CPU, along with a simple time-synchronization mechanism that "just works ". However, these are just plans, not products :(
Created Date: April 19,2011
Created by: clintonp
Franji,
Are you saying that it simply can't be done? I can't send a request packet to a specific IP address on the network, and receive a repsonse from it?
Paul in WI
Created Date: April 19,2011
Created by: clintonp
Ecom100 / rbe
What about using Read By Exception? Posting the request with RBE to the specific IP address and reading the response? If the timeserver won't give back a UPD/IP packet, what about doing the same thing to an application on a PC that's gotten the time from the timeserver?
Paul
Created Date: April 19,2011
Created by: Do-more PE
It would have to be done from a PC application most likely although there might be a gateway type of device out there that could do it..
The thing to remember here is that Ethernet has 7 layers. Each layer is defined for a specific purpose. See the Wikipedia OSI model entry for more detail.
TCP/IP and UDP/IP reside on layer 4. This layer is responsible for getting data moved around the physical media which resides on Layers 1 and 2. Layer 3 determines how the data is shaped.
Layers 5, 6 and 7 control how the data is formatted or the protocol. MODBUS TCP/IP is one format method. Allen Bradley Ethernet IP is another format method. So is SMTP, HTTP, FTP, etc. Each of these methods are designed to talk specifically to each other and not to interfere with the other possible formats.
Lets take making a phone call as an example. You want to call China. Obviously your phone and the accompanying wireless signal and wires is the physical media (Layers 1 and 2).
The Signal traveling over the wire is similar to Layer 3. Your voice is similar to Layer 4.
The language that you end up speaking to the party that answers is the protocol. If someone answers that speaks Chinese and you don't know Chinese and they don't know English, not much communication is going to take place. (Layers 5, 6, & 7)
Now you can add a translator to try to make this work but if the translator is not very fast or good it can slow down the communications and you may not pick up all the nuances of the conversation.
Hopefully this makes some sort of sense. It's not the best example and I simplified it extremely, but it should give you an idea as to why there needs to be a protocol converter or software wedge in the system to make this happen. Now you can add a translator to try to make this work but if the translator is not very fast or good it can slow down the communications and you may not pick up all the nuances of the conversation.
Created Date: April 19,2011
Created by: clintonp
I'm looking for a push in the right direction for a couple of VERY basic questions.
Using a DL06 with an H0-ECOM100, I have to interrogate a timeserver on the network. I'll have to send it a request, and listen for the response (an NTP time stamp). I don't know where to begin to do the actual i/o. What I have so far is the hardware, and the IP address of the timeserver.
Can someone point me toward documentation of the steps involved in sending the request and picking up the response? I have not read every word of Chapter 4 of the ECOM manual yet ( RLL Programming for Communications ), but it looks like that won't help -- it seems to focus on peer-to-peer PLC communication.
Paul in WI