CiA is committed to use SI units as standardized in the ISO 80000 series. The CiA 890 technical report defines the coding of SI units (international system of units) and prefixes to be used in CiA specifications. The predecessor document (CiA 303-2) was limited to CANopen documents.

This technical report intends to harmonize the coding of SI units and prefixes within CiA documents. If non-SI units are desired, the CAN-connected devices need to convert the communicated parameters to assigned SI units. A typical example is a human machine interface device, for example a display. It communicates a length parameter in meters optionally assigned with a prefix such as “kilo” or “milli” via the CAN-based network. After conversion, it shows the value on the display in “miles” or “inches”, for example. The document also provides a recommendation how parameters for SI units and prefixes should be structured.