Quantum Modbus Redundant link

In modicon hot standby configuration,i want to setup redundant communication link to my scada through modbus ports.In case of failure of one link (means no switching system is still in Redundant mode without any problem) can i able to control through other link connected to Standby Controller.or i have to manipulate CHS command register.how it is possible with reasonable option

You can use counter. HMI do increments counter. PLC compare counter with old value. If counter not change on the few second, PLC write to command register.

thnx for your reply.

Can i read/write coils/registers in standby controller.I read at one place that Primary controller only executes logic and update in standby controller.

You can read anywhere from the standby PLC (it's Modbus / MB+ / IP address is offset from the primary), but writing is a different story.

The hotstandby system is configurable as to what areas are transferred from the primary to the standby controller. Anything in the standby within the transfer area will be overwritten by the primary. By configuring your hot standby properly you can have areas in both controllers that don't get swapped back and forth.

This, by the way, is a 984 view. The IEC hotstandby works a little bit differently since it also has to account for the unlocated variables.

And a quick re-read of your original questions leads me to point out what you want is the "Reverse Transfer Area" that lets you send information from the standby to the primary. You would want to write to that area in the standby, and then have logic that looks at some point within there to switch control from the primary coils to the ones within the standby reverse transfer area.

You could, by proper programming of the command register, force the hot standby system to transfer from the primary on a communications failure.