I have a question about ControlLogix slots - are they all the same? When two cards communicate with each other, does the slot they are in affect the backplane bandwidth? For example, would an ethernet card in the last slot communicating with a controller in slot 0 have a different impact compared to an ethernet card in slot 1 communicating with a controller in slot 0? Additionally, the manual for redundant 1756-EN4TR specifies that the cards should be in slot 0 and 1 - is there a specific reason for this slot requirement? Thank you, Trevor.
The ControlBus backplane in a 1756 chassis is not limited by distance or slot placement, but may be affected by power requirements when using hydraulic control modules or Prosoft MVI's. While it has been a common practice for over 20 years to place communication modules next to the CPU in Slot 0, there is no technical obligation to do so. There is nothing inherently special about Slot 0 and Slot 1 in terms of functionality. The recommendation to use Slot 0 and Slot 1 for 1756-RN4TR modules in Redundant Adapter Pair setups likely stems from convention that evolved into a mandatory rule. This setup may be designed to mimic the "IP plus one" network address allocation for paired -EN4TR modules.
As Ken pointed out, the key requirement for setting up a Redundant Adapter configuration in an IO rack is that modules must be placed in specific slots in order to communicate with each other effectively.
I appreciate the feedback from Ken Roach and Contr_Conn, which supports my current belief. I am considering testing various unsupported slot configurations for the redundant Ethernet adapters. While reviewing the Ethernet manual, I came across a screenshot showing the adapters in the same chassis as the processor (although the processor was in slot 2), despite the manual specifying that only IO cards can be in the chassis with a redundant pair of EN4TR cards. It would be ideal if there were no slot requirements. I plan to explore the CIP messages used to configure the cards into redundancy and see if I can manually set them up in different slots.
I strongly advise against making architectural decisions based solely on illustrations. It is important to rely on engineers or documentation authors to avoid inconsistencies. If you come across any inconsistencies, consult with RA or other experts. I do not have experience with the -EN4T, but it appears to be a new hardware platform with unique features such as adapter teaming, pairing, and redundancy.
Certainly, I am intrigued to explore the feasibility of implementing certain features. Utilizing products that are already integrated makes it simpler to request support from our Rockwell representative. The EN4TR units have proven to be highly reliable in my previous projects, which is why I now incorporate them into all new projects. I am particularly optimistic about the possibility of dual IP support being introduced in future models. Although the hardware currently supports it for PRP functionality, the end user interface for this feature is not as accessible as it is on the CompactLogix.
Hi Trevor, great questions! All slots in a ControlLogix chassis have the same backplane bandwidth; however, the trick is in how the data gets routed. If an ethernet card in the last slot communicates with a controller in slot 0, the data has to travel across every slot until it reaches its destination. Putting a card in the first available slot after the controller makes the communication a bit more efficient as it shortens this transit so to speak. As for the 1756-EN4TR redundancy requirement, it's because these particular cards are designed to work in pairs to provide fault tolerance, and the slots 0 and 1 set-up ensures that the back-and-forth communication between these two cards is as quick as possible.
Great questions, Trevor! While all slots in a ControlLogix chassis are fundamentally the same in terms of their ability to host cards, their position can affect communication paths and backplane bandwidth to some extent. The backplane is designed to be high-speed, but certain configurations may optimize performance; for instance, having an Ethernet card in slot 0 might provide a slightly more direct route for data since it can minimize the distance signals have to travel. As for the redundancy requirement in the 1756-EN4TR, placing cards in slots 0 and 1 ensures that the redundancy management process is efficient and reliable, as these slots are typically prioritized for critical communications and device synchronization. Just something to keep in mind for maintaining optimal system performance!
Hi Trevor! Great questions about ControlLogix slots! While all slots can support various cards, their physical position can indeed influence communication speed and backplane bandwidth due to how data routes across the backplane. Generally, receiving data from cards positioned closer to the controller (like slot 0) tends to offer slightly better performance than those farther away. As for the redundancy requirement for the 1756-EN4TR, placing them in slots 0 and 1 likely ensures optimal synchronization and redundancy since the system is designed to prioritize communication between those slots for quicker failover. Always a good idea to stick to manufacturer recommendations for those setups!
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Answer: 1. Are all ControlLogix slots equal in terms of backplane bandwidth and communication impact? - No, the slot position of cards can affect backplane bandwidth when communicating with each other. 2. Does the slot position of cards impact communication between them? - Yes, the slot in which cards are placed can impact communication, especially when communicating with controllers in different slots. 3. Why does the manual for redundant 1756-EN4TR specify that the cards should be in slot 0 and 1? - The specific slot requirement for the redundant 1756-EN4TR cards is likely to ensure optimal communication and performance.
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