AB ControlNet latency

stinklizard · Jul 17, 2017

I am putting together a 1756 platform (1756-L1/M2 and 1756-ENBT), and was wondering if anyone had some numbers for the ControlNet polling speeds as the quantity of nodes increases. If for instance, if I had 18+ 1794-ACN15 modules: what would the token time be for a full rotation of reading/writing all devices on the ControlNet.

If I use cat5, it will be segregated from other networks. This should be considered a medium noise environment, and the distance for all devices is less than 33 meters. I will use cat5 shielded, as well.

I've read the ControlNet configuration manual (http://literature.rockwellautomation.com/idc/groups/literature/documents/um/cnet-um001_-en-p.pdf), and could not find the effects to time of scaling up.

Ken Roach · Jul 17, 2017

Welcome to the PLCTalk Forum !

First, understand that ControlNet uses co-axial RG59 cable and purpose-built taps and terminators. It does not use twisted-pair CAT5e cable like Ethernet does. The RJ45 style connector on the old ControlNet modules is not an Ethernet connection; it actually dates from the late 1990s and is a "ControlNet Network Access Port" for plugging in a ControlNet network interface card.

Your 1756-L1 controller is a first-generation unit; it can't be upgraded to any version of firmware whose associated software is officially compatible with Windows 7 or Windows 10. Not that it won't work for your application: just be aware that you might be running some older software.

My conservative rule of thumb for discrete I/O on ControlNet has always been about 2 milliseconds per adapter. You can do a little offline estimation of network utilization in RSNetworx for ControlNet software, but it's been a while since I did that.

Are you expanding an existing system, or putting together a new one out of older parts ?

stinklizard · Jul 17, 2017

I am putting together a system from scratch, purely for learning purposes... eBay is almost making this not break my bank. The last time I learned to program was on the SLC-500, so I won't pretend to know what I'm doing. I'm taking classes at a college which I'm told can plug in to any firmware (13 in this case). The documentation is not very clear, so I appreciate you telling me about the coax cable. The documentation appeared to say control net would work on multiple mediums. But luckily I've used a lot of Siamese cable for security system installations.

Should I opt for devicenet? The teachers don't really have many answers for much past "the basics". Again, Rockwell doesn't have documentation in a format which is easy for someone unfamiliar with the platform. I appreciate your information

Ken Roach · Jul 17, 2017

If you're trying to keep things simple for learning purposes, you should stick with EtherNet/IP networking.

It requires no additional RSNetworx software, uses common and inexpensive twisted pair cable.

DeviceNet is great if you're willing to read the manuals and pay attention to the physical layer, but not if you're just putting something together to learn the basics of ControlLogix.

stinklizard · Jul 17, 2017

Sound advice. I will start on the child end of this and work my way up to the adult level. I don't mind crawling before I run.

Andybr · Jul 18, 2017

Ken Roach said:
Welcome to the PLCTalk Forum !

First, understand that ControlNet uses co-axial RG59 cable and purpose-built taps and terminators. It does not use twisted-pair CAT5e cable like Ethernet does. The RJ45 style connector on the old ControlNet modules is not an Ethernet connection; it actually dates from the late 1990s and is a "ControlNet Network Access Port" for plugging in a ControlNet network interface card.

Your 1756-L1 controller is a first-generation unit; it can't be upgraded to any version of firmware whose associated software is officially compatible with Windows 7 or Windows 10. Not that it won't work for your application: just be aware that you might be running some older software.

My conservative rule of thumb for discrete I/O on ControlNet has always been about 2 milliseconds per adapter. You can do a little offline estimation of network utilization in RSNetworx for ControlNet software, but it's been a while since I did that.

Are you expanding an existing system, or putting together a new one out of older parts ?

We run a number of old systems with L1 processors and V13 firmware in our plant and I can confirm that it is possible to install V13 of Logix 5000 on a Windows 7 system if you ignore the error messages you will get during the process. Once installed it will work reasonably well but there are some things which do not work as intended. An example is that the "pop up" used to select a specific bit from a DINT does not show the correct bit numbers though it will return the right bit if you just count up from bit 0. You also need to bear in mind that there were some major changes to the structure of timers (and probably other instructions) when the L1 processors were superceded which can cause compatibility issues if you need to update a programme for use with a newer processor.

stinklizard · Jul 18, 2017

Andybr said:
We run a number of old systems with L1 processors and V13 firmware in our plant and I can confirm that it is possible to install V13 of Logix 5000 on a Windows 7 system if you ignore the error messages you will get during the process. Once installed it will work reasonably well but there are some things which do not work as intended. An example is that the "pop up" used to select a specific bit from a DINT does not show the correct bit numbers though it will return the right bit if you just count up from bit 0. You also need to bear in mind that there were some major changes to the structure of timers (and probably other instructions) when the L1 processors were superceded which can cause compatibility issues if you need to update a programme for use with a newer processor.

Does that include running the program in compatibility mode? Granted I am using a school's license on XP, I am just curious.

Andybr · Jul 18, 2017

No. Our corporate rules do not allow VM's so I have to run it on Windows 7.

AB ControlNet latency

stinklizard

Member

Ken Roach

Lifetime Supporting Member + Moderator

stinklizard

Member

Ken Roach

Lifetime Supporting Member + Moderator

stinklizard

Member

Andybr

Member

stinklizard

Member

Andybr

Member

Similar Topics