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suma

I/O scanning in Quantum hot standby system

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hi all... I am having a quantum hot standby sytem,i want to collect the data from another system having 140cpu 65150.I heard like through i/o scanning it can collect the data.I dont have any idea in this plz guide me how to do this one? regards Suma

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You can't make 2 PLCs talk through I/O scanning. That's for one PLC to talk to remote racks (with CRA adapters, not full PLCs with CPUs). Look at networks like Modbus Plus or Ethernet.

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Dear crossbow, thanks for your reply have doubt again.. IF am having NOE in both the setup's then also its not possible to collect data through I/O scanning! and what is mean by bumpless switchover? regards suma

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You are not referring to making the two PLCs in the reundant system talk right? That's not possbile, that's what the hot standby system does. But if you are trying to use the redundant system and communicate to another PLC, the networks are the way to go. I/O scanner is for remote I/O. As I stated before, it is not for making two controllers talk to each other. You can use commands in the PLC program to read and write data across the network. I/O scanning is for communication to devices without CPUs, like Momentum I/O bases or remote racks over Modbus Plus. Bumpless switchover means if one PLC crashes (hardware or software error) the other will pick up immediately and run the process, without a loss of control. The two PLCs in the redundant system are processing the same program at the same time, so if one fails, the other controls the same I/O as if it was the first. The addresses (Modbus Plus and Ethernet) will automatically swap too, so a SCADA system or operator interface won't notice the change of CPUs.

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Thanks Crossbow, Really i got a meaning for bumpless switchover but still am having some doubts in I/o scanning i reed some reference manual but it seems like you can tranfers data configured in network and also you do the same by using Master/slave concept another one is MCR function block.please brief me this concepts. thanks in advance regards suma

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I have nothing further to say on the I/O scanner. It's for dumb devices like Momentum terminal blocks, not for PLC to PLC communications. You need to use the commands to perform data transfer between PLCs. As for the MCR block, never heard of it.

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Actually, IOScanning IS the correct term for what you want to do. The name can be a bit confusing, since it's not actually IO that you're talking to in this case, but you're on the right track. IOScanning is a method of talking between two ethernet devices - in this case your CPU in the hotstandby system and the other CPU. A CPU can read and/or write data from/to an 4XXXXX (%MW in Unity) area in another ethernet CPU or device. It CAN be used to get IO data from Momentum bases that are equipped with ENT communication heads, which probably is where the IOScanning name comes from, but it can also be used to move data between two PLC's, which is what you want to do. It's only real limitation is that it can only read and write to 4XXXXX (%MW) addresses, so you can't directly read coil status information in a remote PLC - it has to be moved into the proper memory areas. The IOScanning is controlled by a table that you build using the programming software. In Concept and ProWorx it's a configuration extension, but I don't remember where it is in Unity. You fill in the IP Address of the remote PLC, the rate you want to read and or write, and the addresses within the local and remote PLC's that the data moves from or to, along with the number of words. There are some limitations, including (I think) a 500 word total limit on words moved. There are WAY more details than that, but that should point you in the right direction. As a bit of fill in: On a Quantum PLC you could have the following communications: IO - This is IO that is in the local PLC rack or in a remote rack connected via coax cable. It uses the S908 protocol (for the remote stuff) and is scanned between 984 ladder segments (or at the beginning of the PLC scan in Unity). That's probably what the other poster was thinking of. PeerCop - This is a Modbus Plus communications for communicating between PLC's or for talking to Momentum IO bases. It uses the Modbus Plus port on either the CPU or the NOM modules, and must be configured in pairs (the remote PLC must have a matching entry). Momentum IO bases have a default PeerCop setup in them when on a ModbusPlus comm adapter. There are two types of comms under PeerCop - Global and Specific. Global, as you might guess, is one to many, and Specific is one to one. IOScanning - What I described at the beginning. This uses ethernet to talk between PLC's or from a PLC to an ethernet device, like an IO base or communications bridge. HotStandby - the hotstandby pair of PLC's constantly talk over their fiber connection, and you can use the reverese transfer area to move data from the standby PLC to the primary PLC. There are messaging instructions, like the MSTR block in Concept / Proworx, that can talk either via the Modbus+ network or the ethernet network, to move data from PLC to PLC. There are the equivalent under Unity. There is also an XMIT instruction that can use the Modbus port on the CPU as a Modbus master to get data from other Modbus slave devices, using serial Modbus protocol. And, of course, there are other add in modules that support other protocols, like Profibus etc. Hope that helps Ken You could, by the way, make the hot standby processor pair talk via ethernet, but it requires a really good knowledge of how the hotstandby system works. You can setup the hotstandby system so that not all of the memory is copied from the primary to the standby via the fiber system. Then you could configure an entry in the IOScanning table to push data from the PLC to the device at the next IP addresses up (which is where the standby PLC will be) and push into this non transfer area. You could also use messaging blocks to do this, but you have to pay attention to which sections are executed by the standby. Of course, it would be easier to just let the standby system move the data - primary to standby just happens as part of the system, and the hotstandby supports a reverse transfer area that moves data from the standby to the primary. Edited by plcken

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Thank you Dear, Really i got a very big confident after seen your reply,basically am in begging of the project now designing is going on,earlier i discussed with lot of guys thy said no issue start the design definetly its possible through ethernet network.Now your wordsd are boosting much for me ... thanks again... regards suma....

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