MARWIS-UMB
Operating Manual V 3.3 / 9 Dec 2019
20.3 CAN Protocol (Version 1.0)
20.3.1 General remarks
All Marwis measuring channels can communicate over the CAN interface. Each value will be
sent in its own CAN telegram.
In order to transfer a measured value it is either possible to send a remote telegram which will
cause the value to be transferred once or to configure a trigger so that the value is sent
automatically time and time again. In this latter case the system will check once every 10 ms if a
value is supposed to be transferred. The configured triggers of the CAN data transmisison are
stored permanently, i.e. need to be configured only once when commissioning a MARWIS-
UMB / STARWIS-UMB.
Each end of the CAN bus should be terminated by a 120 Ohm resistance.
20.3.2 Pin assignment
Pin assignment of the CAN interface on the 8 pole screw plug socket
Pin 1: CAN-High
Pin 4: CAN-Low
20.3.3 CAN-Parameter
The bitrate is 500 kBps.
Extended CAN-IDs (EID) are used.
20.3.4 Data format and byte order in the communication protocol
LONG:
LowLowByte LowHighByte HighLowByte HighHighByte
INT:
LowByte HighByte
FLOAT:
Acc. to IEEE format (4bytes)
20.3.5 Data transmission
20.3.5.1 CAN-ID
Every value will have its own CAN ID. The default values correspond to the UMB value
numbers. Since extended CAN IDs are used, the IDE bit is set in addition.
Examples:
Value
Value number
(dez. / hex)
11 Bit
Identifier
(hex)
IDE
18 Bit
Identifier
(hex)
RTR CAN-ID
(extended)
Road temperature in °C
100d = 0x0064h
0x000
1
0x00064
0
0x00000064
Water film height in µm
600d = 0x0258h
0x000
1
0x00258
0
0x00000258
Road state
900d = 0x0384h
0x000
1
0x00384
0
0x00000384
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Chapter 20, Appendix
