Basic Function Principles
The KM6551-0000 data exchange module enables the wireless exchange of data between two or more controllers. It uses the IEEE 802.15.4 standard as its basis with a Beckhoff-specific protocol. 10 bytes of user data are transmitted per data packet. The DIP switch is used to set the operating mode of the KM6551-0000, i.e. whether the module functions as a master or slave and which communication mode is to be used.
The data is exchanged in the peer to peer and master-slave modes using the polling method. In broadcast mode, one module is the broadcast master that sends the data and all other modules are broadcast slaves that receive the data but cannot send data to the broadcast master themselves. Hence, they listen only to data from the broadcast master.
In master-slave mode you can decide via the software with which slave data should be exchanged. Up to 7 slaves can be addressed.
The data exchange module KM6551-0000 supports 16 channels, which are freely selectable and can be used, for example, to establish several radio networks or for placement outside WLANs or other radio systems that also use 2.4 GHz.
The KM6551-0000 can scan the possible 16 channels. The energy in the frequency range is measured to ascertain in advance whether other systems are active and on which frequencies. Furthermore, the so-called LQI (Link of Quality Index) is transmitted with each data telegram. This makes it possible to determine the quality of the signal. A high LQI value indicates a good connection, a low value a poor connection. In order to improve the LQI value, a larger antenna or an antenna with a correspondingly larger transmission factor can be used.
Communication mode
The KM6551-0000 data exchange module supports three different communication modes.
Mode 1: Peer to peer – data exchange between two modules
Enables the exchange of data between two KM6551-0000. A maximum of 10 bytes of data can be transmitted per cycle. In one cycle (typically < 20 ms), module 1 sends data to module 2 and module 2 sends data back to module 1.
Mode 2: Master-slave – data exchange between a master and up to 7 slaves
In master-slave mode the master can communicate with up to seven KM6551-0000 using the polling method. To do this, set the corresponding slave addresses using the DIP switch. From the PLC you can inform the master which slave it should communicate with, how often and for how long. Approx. 20 ms are required per slave. For seven slaves this results in a minimum cycle time of 140 ms which the master requires in order to address all 7 slaves once each.
Mode 3: Broadcast to any number of slaves
In broadcast mode, only the broadcast master transmits. All other modules (broadcast slaves) can only receive data but cannot send data themselves. Any number (x) of broadcast slaves can listen in.
 | Support of the KM6551-0000 using Bus Couplers, Bus Terminal Controllers and TwinCAT The KM6551-0000 is supported from TwinCAT 2.10 Build 1326 onwards. The following Bus Couplers are supported: BK1120, BK1250, BK2020, BK3120, BK3150, BK9000, BK9050. (Further Bus Couplers on request). All Bus Terminal Controllers from the BCxxxx, BXxxxx and BXxxxx series are supported. |
The CE conformity of the KM6551-0000 is only guaranteed if it is operated with original Beckhoff accessories (antennas, coaxial cable)!