PROFIBUS DP/FMS Redundancy Link Module RLM02

Field devices equipped with only a single PROFIBUS DP interface can be integrated in the redundant PROFIBUS network by using the Redundancy Link Module RLM02.

The RLM02 converts a nonredundant PROFIBUS line to two redundant RS485 lines or vice versa. You can position the module directly after a master, before a bus segment with several slaves or before an individual slave. PROFIBUS stations with redundant couplers [K] can be directly connected to the PROFIBUS set redundant by RLM02.

Stations with only one interface can be optionally assigned to the A or B line. Each RLM02 PROFIBUS interface can serve up to 31 PROFIBUS stations. Using repeaters [R] and media converters [O/E] makes it possible to increase the length of the PROFIBUS lines and the number of stations.

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Field devices equipped with only a single PROFIBUS DP interface, can be integrated in the redundant PROFIBUS network by using the Redundancy Link Module RLM02. Acting like an active switch, it converts two redundant lines to one PROFIBUS DP line or vice versa. The RLM02 amplifies signal form and amplitude of the incoming data and monitors activities and error statuses of all three lines.

RLM02 at a glance:

  • Three PROFIBUS ports
  • Transparent for PROFIBUS configuration, i.e. no slave address required
  • Supports transmission rates of 9.6 kbit/s to 12 Mbit/s
  • Serve up to 31 Profibus clients. While using repeaters (optical - electrical), this number can extend
  • Errors are signalized via an LED on the front plate and a signaling contact
  • Specific messages that can be read at the 8-pin terminal strip serve diagnostic purposes
  • CE, UL and CSA certified
  • Type Approval Certificate "DNV GL" for use in marine area.  
Conversion of one simple, non redundant PROFIBUS line into two reciprocally redundant lines A/B and vice versa.

  • Use on PROFIBUS DP/FMS lines
  • Automatic line selection
  • Transmission rate 9.6 kbit/s .... 12 Mbit/s
  • Communication Monitoring
  • Repeater functionality
  • Wire cross section 8-pin terminal strip, up to 1.5 mm²
  • Redundant power supply, 24 VDC (+20 .. +33 V), 120 mA typically at 24 V
  • Operating temperature 0 ... 50°C
  • Status and error display
  • Power supply monitoring
  • Potential-free signaling contact
  • Easy assembly on a DIN mounting rail 
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.


Line redundancy:
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. 

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