Nodes are not consumed "on the fly"...
GaryS said:
Just for the record the information I posted came from a conversation I had with rockwell on just that problem...
Yes, before I posted I had specifically recalled that you had originally learned this information from a Rockwell representative. I cannot speak for that individual, nor do I want to appear to doubt their knowledge on the subject. However, I do think it is possible that they did not fully understand the newly introduced feature of counting Ethernet Nodes for a controller as opposed to the older method of counting Connections. I have also had several encounters with Rockwell Support Engineers where, when I felt I knew better, I have had to correct them on small but important interpretations of product functionality. One elementary example in recent times was an issue with an SLC Typed Read message which was timing out to another controller. They started by asking how was the Write message configured in the other controller, to which I of course replied there is none. They then said that was my problem. I then said could I please speak to an experienced SLC Support Engineer?...but of course I also went on to explain their misunderstanding of how it should work.
I have also previously, and today, considered the possibility that what they had said, and what you believed them to have said, may not be exactly the same thing?
GaryS said:
...if memory serves it was an L16 and it was limited to 6 nodes we added another drive and started seeing the problems...we were dropping network devices at random I called...
If you were trying to add 6 Nodes to an L16ER then you would certainly be seeing problems. I think I mentioned the Node limit of "4" for the L16ER at least half a dozen times in my previous posts here? The software would not allow you to compile a 6 Node L16ER project and download. Your troublesome project could only have been at maximum a 4 Node L16ER. If you physically provisioned more Ethernet I/O devices onto the network, like Ethernet drives, without them being allowed in the project and hence the controller not knowing about them, then there are scenarios which could have caused interference with the existing valid configuration. But we won't go into that cold case here.
GaryS said:
...the infrmation was as I stated and they indicated they the programmer pc uses 2 nodes...
Again, I believe strongly that this is incorrect. Connections, perhaps? But not Nodes.
GaryS said:
...i thnk its RSLinx and RSLinx Enterprise both are running on the pc when you are connected...
You also originally stated this and it is also incorrect. When you connect to a Logix 5000 controller you are using an RSLinx Classic communications driver. RSLinx Enterprise (now FactoryTalk Linx) is primarily used for HMI communications, be it from a computer "Station" based application to a controller, or from a physical HMI terminal to a controller. It may also be used for communicating with any FactoryTalk Live Data capable device or application. RSLinx Enterprise will not establish a connection with a controller simultaneously with an attempt to go online with RSLinx Classic. They are totally independent.
If you happened, for instance, to have a FactoryTalk View ME Station application running on the workstation computer, then RSLinx Enterprise could possibly be communicating with the controller. However, even if both were running and simultaneously connected to the same 4 Node controller, they would only be using controller Connections, and not any of the Node count.
To clarify this further...
The controller knows nothing about "Nodes" or how many are allowed, used or remaining. All it knows is "Connections" and how many are allowed, used or remaining. If a 4 Node limit is used up, all the controller sees is how many Connections have been consumed. If other non I/O devices are also using Connections then all it sees is the total Connections in use and what is remaining. It will keep opening Connections to devices, of all types, until it has no more.
The Node limit feature and restriction is entirely in the software on your computer. This just prevents us from compiling and downloading a project with too many I/O devices added to the I/O tree, which could consume too many of the available Connections, and leave very few or not enough Connections for non I/O devices which may be added now or in the future.
Another point, which hopefully sets aside the notion of communications software on our computers decreasing this Node count...
As the Node limit is only in the software, the Node limit verification is done at compile time and before downloading and running the project on the controller. It is not checked at any other time. Therefore, an "after the fact" attempt to connect to a running controller from RSLinx Anything cannot and will not have any effect on a virtual Node count that is only performed when a project is being compiled for download i.e. Nodes are not consumed "on the fly".
When the project is being compiled, any connected device that is not added to the I/O Configuration (workstation computer) will not go against the Node count. If you are compiling an otherwise valid L16ER project, and there are 4 Nodes added, then you may proceed to download. Nothing on a running controller can change this at a later point.
Nodes are "virtual" within the programming software and used to limit how many Connections will be used for I/O devices when the controller is running.
Connections are "real" within the controller and they will be consumed by both the devices (Nodes) added to the I/O Configuration and the devices not added to the I/O Configuration, up to the total Connections for the controller.
GaryS said:
...programming computer will take up 2 nodes...the programmer pc uses 2 nodes...
So again, the Node limit is only verified when a project is being compiled, and never when we make a connection from a workstation computer. They cannot use or take up 2 Nodes.
Interestingly, I found your very first statement on the above and you had actually said this...
GaryS said:
...Don't forget the programming PC uses 2 connections, RSLinx Classic and RSLinx Enterprise...
You said "connections"?
But then went on to state this, 2 posts later...
GaryS said:
...Check the manual the L16 only supports 4 nodes and the PC will use 2 of those.
what will happen is the L16 will start dropping connections different devices at different time it will drive you nuts
you should make another processor for this project....
Whatever about Rockwell, you appeared to be confusing or interchangeably using both terms as though meaning the same thing?
In all your statements I've read, if we substitute "nodes" with "connections" then they tend to make a little more sense?
Original thread for reference...
Only 4 Ethernet/IP Nodes on a CompactLogix 1769-L16ER-BB1b ?
Regards,
George