Control/CompactLogix - Produce / Consume - How specific does the peer need to be?

[kdcui]

I currently have a setup in Siemens S7 using I-Device connections over PROFINET and I am trying to investigate an equivalent setup using Rockwell. It has been several years since I have used Produce / Consume tags and had a few questions.

In my scenario I have 2 controllers:
PLC A
PLC B

The issue here is that many instances of PLC B will be connecting (only 1 at time) to PLC A. All instances of PLC B will be identical (PLC type, firmware, etc.).

Can I set up produce / consume tags between A and B that will still work when different instances of PLC B connect to PLC A? Essentially, PLC A will remain the same but different instances of PLC B will connect, and I want communications to resume upon reconnection. I was not sure if there was a unique identifier associated with the physical hardware that would prevent this.

As a follow-up:
Is there a way to send safety data between 2 GuardLogix controllers? Siemens has Flexible F-Link over PROFISafe

Thanks!

 

[Jeev]

First Question:
If you are talking about Producing on PLCA and Consuming on multiple PLCB's then yes you can specify a number of maximum consumers. I would also check to make sure you are not going over the ethernet node limit on PLCA when adding all those PLCB devices.

Second Question:
Yes. You can do Produced/Consumed safety tags too.

 

[joseph_e2]

...
Second Question:
Yes. You can do Produced/Consumed safety tags too.

I'm not dealing with this right now, but I'm curious. Can the consuming safety PLC use the consumed safety tags in its own local safety program and maintain safety performance level? I have a future (hoped for...) project where it could really simplify things for me.

 

[Operaghost]

I currently have a setup in Siemens S7 using I-Device connections over PROFINET and I am trying to investigate an equivalent setup using Rockwell. It has been several years since I have used Produce / Consume tags and had a few questions.

In my scenario I have 2 controllers:
PLC A
PLC B

The issue here is that many instances of PLC B will be connecting (only 1 at time) to PLC A. All instances of PLC B will be identical (PLC type, firmware, etc.).

Can I set up produce / consume tags between A and B that will still work when different instances of PLC B connect to PLC A? Essentially, PLC A will remain the same but different instances of PLC B will connect, and I want communications to resume upon reconnection. I was not sure if there was a unique identifier associated with the physical hardware that would prevent this.

As a follow-up:
Is there a way to send safety data between 2 GuardLogix controllers? Siemens has Flexible F-Link over PROFISafe

Thanks!

As for a unique identifier, that would really just be an IP address. There is really nothing unique beyond that the PLCs will care about.

I guess we should ask if the data exchange is bi-directional. If PLC A is producing data and not consuming, then things are a whole lot easier. PLC A doesn't care who is consuming the data it is producing. It doesn't care who PLC B is, or if PLC B even exists. You don't need to place the PLC B controllers in the I/O configuration for PLC A or anything like that. But PLC A would need to know the maximum instances of PLC B that might need to consume data at a given time. Then you can specify in PLC A how many consumers there will be.

If the data exchange is bidirectional then that gets trickier. Any PLC that will be consuming data must place the producing PLC in their I/O Configuration. As such, these producing PLCs are handled similar to any other I/O module. They would exchange data based on an RPI setting and if communications were lost, it would be treated as a module fault. You don't necessarily turn this communications on and off (although it can be done).

I don't really get involved in safety systems so I can't speak to the safety aspect especially the performance, but produced and consumed tags must be controller-scoped. So the local safety program can use those tags, but so can any program in the controller. They wouldn't be unique to the safety program only. But as they have certain safety-related options for consumed tags, I would guess they meet the performance requirements. But someone with more safety experience might be able to shed some additional light.

OG

 

[JeremyM]

Couple things about swapping the PLC (in case it isn’t a safety model):
- Safety can produce/consume safety and standard tags.
- Standard can produce/consume standard.

If the connection is keyed against mismatched hardware, it won’t work.

 

[L33er]

Does it really matter? Standard can produce/consume to safety plc. And vice versa.
There’s safety mapping tags

 

[Jeev]

I'm not dealing with this right now, but I'm curious. Can the consuming safety PLC use the consumed safety tags in its own local safety program and maintain safety performance level? I have a future (hoped for...) project where it could really simplify things for me.

Yes, that's what they're intended for. In short, Safe Produced/Consumed tags use CIP Safety to maintain a level of integrity.

The documents you are after for the safety produced/consumed stuff are the GuardLogix Safety Reference Manuals and GuardLogix User Manuals (These provide the capabilities and limitations).

You will need to factor in aspects like reaction time and you will need to check if the producing controller being turned off results in the behaviour you require.

 

[joseph_e2]

Yes, that's what they're intended for. In short, Safe Produced/Consumed tags use CIP Safety to maintain a level of integrity.

The documents you are after for the safety produced/consumed stuff are the GuardLogix Safety Reference Manuals and GuardLogix User Manuals (These provide the capabilities and limitations).

You will need to factor in aspects like reaction time and you will need to check if the producing controller being turned off results in the behaviour you require.

That's really good to know, thank you!