The RLM02 module can be positioned directly next to a master, in front of a bus segment with several slaves, or in front of an individual slave. Several PROFIBUS stations with redundant couplers can be connected directly to the PROFIBUS that has been made redundant by RLM02. Stations with just one interface can be positioned either on the A line or on the B line. Each RLM02 PROFIBUS interface can operate up to 31 PROFIBUS stations.
The module reinforces the signal form and amplitude of the data received and monitors all three lines with regard to activity and faults. Any faults that are recognized are indicated with the aid of a LED on the front panel. Suitable messages are available for diagnostic purposes and can be picked up on the 8-pole terminal strip.
Combining redundant lines:
The data that arrives first via line A or line B, with the correct start of frame, is forwarded to connection M. If the data arrives at the same time, either line A or line B is selected at random. If an error is detected at line A, the control logic switches to line B, which is still available. The procedure is the same in reverse for line B.
Splitting a non-redundant line:
Data arriving via line M with the correct start of frame is passed in parallel to the other two connections, A and B. If the start of frame is incorrect, the control logic does not output any data at A and B.
For increased availability of the RLM02 itself, a redundant power supply with 24 V d.c. can be connected. The monitoring logic checks whether both voltages are available and reports any malfunction that may occur. For a single supply of RLM02, the L2+ terminal has to be bridged with the second L1+ terminal.