Read PM864/PM865/PM866 status through alternate COM
I am using the processors above in a redundant PLC configuration (not redundant network though) and I want to read PLC status and optional PLC variables.
First option would be COM2 - Ethernet but as far as I know I can use this only with ABB tools or OPC servers, just like COM1.
Second option would be COM3 - Modbus communication but this port is available only as MASTER and I cannot poll anything from it with a custom made PC software. Is this true?
Do you guys know any other possibility of reading PLC status with a custom tool? I need this to centralize PLC info.
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> "I am already using ABB OPC for the main automation purpose on site, but connecting to that OPC server over the internet requires OPC tunneling and other DCOM and security setting which I am not willing to modify just to get PLC status over internet. "
OK, so this is the real problem. I agree that OPC tunneling and messing with DCOM settings are not optimal. However, writing some other interface to the PLC still leaves you with the problem of getting that data across the internet and back to your monitoring system - as well as leaving you with a non standard solution for collecting system status data.
For status monitoring you do not need to connect to the 800xa "OPCDaSurrogate" server, which is the OPC server for the entire system - you only need to connect to the "AC800MC_OpcDaServer" which is the OPC server that connects only to the PLC. This server is installed on your connectivity servers, but you can install another copy on another PC and open up DCOM or use tunneling only on that PC.
> "Or maybe there is a local client solution that can send data over internet without changing all the security and DCOM settings?"
Yes, theres probably several alternatives, and I think this is the way to go. For example an OPC to SNMP convertor would presumambly be more usefull for a status monitoring system. Google for "OPC to your favourite status monitoring comms protocol"
COM1 and COM2 are Ethernet
COM3 and COM4 are serial. COM4 is used as console port during initial bootup sequence.
MMS Access Variables can be read/written via COM1/2 from a peer implementing the MMS protocol over Ethernet.
Apart from onboard hosted Modbus via COM3/4 you also have the external ModbusTCP (CI867) CEX module but I'm uncertain about possibility to run CI867 as slave.
With proper skills you can craft own protocol with the TCP or UDP standard libraries and use COM1/2.
Why can you not just pull this data from the OPC Server ?
The OPC Server software comes bundled with the Control Builder programming tool ( unless you have 800xA when it is bundled with the 800xA system ). In either case, you already have a copy. OPC is an open protocol that can support multiple clients - so adding an external system status monitor is quite possible.