Modbus network configuration

Hello H-H,

2- ModbusTCP can be used to transfer 2k, a single PN CPU would need about 1 second. But with an H-systems you will get a significant low data rate.
The problem is the redundancy. The main task of a redundant system is redundancy, not communication.
The limitation of 125 registers per telegram is not the ideal solution to transfer 2k, but you must find a communication solution which is supported by both systems.

3- ModbusTCP communication via CP443-1 is slower than via the integrated ethernet interface of a PN-CPU.

4- In your case the gateways must act as ModbusTCP client and ModbusRTU slave. PCS7 is ModbusTCP server and the DCS is ModbusRTU master.
When a server is capable to hold two TCP connections simultaneously, two clients can be connected to it.
Does the DCS support ModbusTCP as well? That would be faster than converting from Modbus RTU to ModbusTCP.

5- Both ModbusTCP redundant libraries - the one for CPs and the one for PN CPUs - are capable of hot standby, requests are processed simultaneously via all projected connections.

H-H

In RTU redundant networks, the PLC acting as slave doesn't have any code to manage the redundant data. I mean it's just moving the required data to both CP341 and the DCS with RTU Masters is tho one who's taking care of redundancy and switching over. 

Will it be the same with Modbus TCP (If the H system is the server)?

 yes

H-H

Do I have to configure the client in DCS to access two servers? 

 That depends on the requirements on site. 

H-H

Referring to the Modbus TCP PN RED wizard in the double sided connection and supposing my H station will be the server, does each client communicate to the two servers?

 

 Is there one ethernet (physical cable) or two? If there are two ethernets and both IP addresses of the DCS are connected to both ethernets, you need double sided redundancy.

When you connect two redundant systems, you usually need double sided redundancy. When a non redundant system is connected to a redundant one, it is single sided redundancy

H-H

What if the configuration is as per my attachment? Do I still have double sided connection in this case or two single sided?

 Does the green line mean a cable or a logical connection?
 I expect that there are some switches as well...

The sketch does not show redundant data transfer. If gateway 1 and master 2 fail, there will be no data transfer at all. It is just redundant data management.

 Regards,
Kaulquappe

It is not possible to have two devices with an identical IP address in one net. IP addresses always must be unique.

Regards,
Kaulquappe

Hello Sorena,
I think you do not use redundant data transfer, just redundant data management. If CP0 is connected only to ethernet0 and CP1 is connected only to ethernet1, you can use identical IP addresses. But FB MODB4H is not capable of hot standby. That means, data are only sent via the active connection.

The new library 6AV6676-6MB30-3AX0 supports hot standby. So you need to order that one.

Regards,
Kaulquappe