Greetings! We currently have a Siemens S7-300 system equipped with 2 Profibus Ports, 4 Remote IO (Wago), and an OP 270. Unfortunately, we are encountering Bus Fault and SF issues on the CPU and all remote IOs. The 4 remote IOs are linked to Port Interface 1, while the Operator Interface is connected to Port Interface 2. The OP features a two-sided profibus connector. In order to conduct diagnostics, we need to connect a PC to the system. However, both Port 1 and Port 2 are already in use. We attempted to connect the PC to the two-sided connector on the OP, but it only detected 1 node and prompted us to provide a rack and slot number without granting access to the PLC. We are seeking guidance on whether we can connect the PC to the two-sided profibus connector on the OP. If so, what PG/PC address should be configured (typically 0)? Additionally, should the profibus termination be set to ON or OFF? We are feeling uncertain and would greatly appreciate any assistance on how to establish a connection between the PC and the PLC for diagnostic purposes. Thank you in advance for your help.
I may be a bit out of practice in this field, but you should be able to easily connect your PC Adapter to the pass-through connector within the system. Remember to turn Termination ON at the final connector on the line, and OFF for all others. The process of connecting your PC adapter should not interfere with this. To set your PC Adapter's address, refer to the "Set PG/PC Interface" option. Personally, I have found it more effective to manually configure the interface instead of using the auto mode, as long as you have the necessary bus parameters in advance. In some cases, I have used the auto mode to gather network settings before switching to manual configuration.
In order to connect your PC adapter to the CPU and go online using Profibus/MPI, you can piggyback onto one of the passthrough adapters attached to the CPU. If those plugs are not passthrough adapters, you may need to remove the plug for the OP270 first. It is important to note that you cannot simply plug into any passthrough adapter to connect and go online unless it is connected to a device that provides power for your communications adapter. Your HMI does not have that capability.
In a forum post, beethoven_ii mentioned the importance of having a device that offers power for your communication adapter when dealing with HMIs. This limitation is crucial to remember when working with S7 systems in the future. Is this restriction applicable to all HMIs or just the operator panels (OPs)? Would the MP or Comfort series be suitable alternatives?
Joseph_e2 mentioned a limitation regarding HMIs, which is important knowledge to remember when working with S7 systems in the future. It is worth noting whether this limitation applies to all HMIs or just the OPs, and if alternatives like the MP or Comfort series would be suitable. It is unlikely that any HMI screens would offer the necessary power for a comms adapter. However, I once collaborated with an engineer who devised a solution by creating a custom lead that could be connected to an HMI passthrough connector. This lead had additional cables attached to provide the required power, which is only 5v. While it has been a few years and the exact method used has faded from memory, this workaround may be worth exploring.
Please specify the model number of the PLC. It is likely that the model is either a 315-2DP or a 317-2DP. To troubleshoot, try disconnecting the operator panel and connecting to the X1 port. The X1 port on a 315-2DP is dedicated to MPI communication, while on a 317-2DP it can be used for both MPI and DP communication.
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Answer: - Yes, you can connect a PC to the two-sided profibus connector on the OP 270 for diagnostics. However, ensure that you follow the correct configuration steps to establish the connection successfully.
Answer: - Typically, the PG/PC address should be set to 0 when connecting the PC to the two-sided profibus connector on the OP for communication with the PLC.
Answer: - The profibus termination should be set to ON when connecting a PC to the system for diagnostics to ensure proper communication and avoid signal reflections that can lead to issues like Bus Fault and SF errors.
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