Modbus TCP/IP in Bailey Infi90
Dear Mr. Murphy,
We are system integrator. The 3rd party systems we are going to use can be configured as Modbus Master so infi90 system must be configured as slave. According to 3 rd party system manuals, for implementing redundant TCP/IP Modbus, different IP addresses shall be used for redundant Masters and same IP address for redundant Slaves. So
1- I set different IP addresses for redundant Masters (please refer to attached diagram)
2- I set same IP address for redundant Slaves.
3- I have to use two pairs of BRC410/HPG800. (Modbus is Single Master and Multi Slaves Protocol, Slaves cannot be shared between different Masters.)
I have not read BRC410, HPG800 and HGS manuals. I have searched for them on the internet but not found anything, if you have them, would you please send me.
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A couple of questions for you regarding the MODBUS TCP Device:
In review of the drawing, it appears that the IP assignments between the Primary Port and the Redundant Port on the MODBUS TCP device are off-set by "1" (e.g. Primary is 192.168.1.3 and redundant is Priamry +1).
Do you know or can you find out if during normal operation if both ports are communicating at the same time or if only the primary communicates and the redundant port only comes on-line when the primary port fails (or it no longer is able to communicate with the other system)?
Or does the MODBUS IP port addressing get handled like it is done with the BRC410/HPG800 where you assign the IP address of the controllers in the interface confuguration (only one number assigned) but under normal operation, only the primary communicates with the interface using the assigned IP address (e.g. 192.168.1.1) and that the redundant module is internally given a "soft" IP address of Primary +1 but upon failure of the primary, they swich over and the Redundant Module assumes the role of primary and the IP address (i.e. 192.168.1.1).
In short, the IP addressing with the BRC410/HPG800 is handled in the same way that the Module addressing is handled with redundant controllers (i.e. the primary has the main address and the back-up has a software address of Module +1 until it becomes active).
Check with the manufacturer of the MODBUS device because this will impact the way that you may need to deal with the interfacinig between the two systems.
Also, please confirm the roles that each side will play in the interface. According to your description, the 3rd party MODBUS device will be the MODBUS "Server" (in the MODBUS TCP world this is called the MODBUS TCP Client) and is the one that will be performing the reads and writes and that the BRC410/HPG800 will be the MODBUS TCP "Slave" (referred to in the MODBUS TCP world as the MODBUS TCP Server) which will be the device written to and read from by the MODBUS device. I ask this only because in about 90% - 95% of the interfaces that our client do, the BRC/HPG is usually the one that is doing the reads/writes from and to the MODBUS device and the implementation that you are discussing is only about 5% - 10% of the ones that we do in the field.
If this is the case, that is fine and the BRC410/HPG800 supports this as well, however, in this role, the BRC410/HPG800 can only support a maximum of 4 of these types of interfaces simultaneously (i.e. acting as the MODBUS TCP Server). Just thought that this might be good for you to know.
By the way, do you have an e-mail address or are you on linkedin? It may be helpful to communicate directly on some of these items rather than through AKS. My linkedin contact page is: http://www.linkedin.com/pub/rob-murphy/13/351/bb8