CI854 Line Redundancy Through DP DP Coupler
I have a CI854, line redundancy enabled. Profibus A goes to a DP/DP coupler with address 2 and Profibus B goes to another DP/DP coupler also with address 2. Profibus A and B are sending identical data out through both lines i.e. line redundancy. On the DP/DP coupler that is connected to Profibus A, on the other side it is the connected to the main IAS interface and Profibus B connected to the backup IAS interface. See attached hand drawn arrangement.
Even though both lines are sending identical data out out, the IAS will only pickup data from one line, mainly from A line, unless that fails it will go to B. The problem starts when IAS send data to the CI854, it only sends on one of the profibus line. If there is a continuous "1" sent on the A line, and the B line is not receving data from the IAS, Profibus B of the CI854 will see a "0" on the same bit due to the DP/DP coupler.
The result is that the CI854 will see two different input data, Profibus A is a "1" and B is a "0". When going online to the control builder, CI854 values changes from 1-0-1-0....
How to configure the CI854 to receive data from either A or B lines without having to rely on the HW error to change it to the healthy channel. Note : The CI854 wil always see both channels as healthy as it is connected to the DP/DP couplers. To the CI854, the slave is the DP/DP coupler.
Thank you in advance if you can help me on this.