CAN dictionary

Explains vocabulary and abbreviations used in CAN technology

Alphabetic selection:


receive error counter (REC)

CAN controller internal counter for reception errors. The REC value IS readable in some controllers.

receive PDO (RPDO)

A process data object that is received by a CANopen device.


A CAN node is called receiver or consumer, if it is not transmitting and the bus is not idle.

reception buffer(s)

Local memory in the CAN controller. where the received messages are stored intermediately.

recessive bit

Bit on the CAN bus lines representing recessive state. It has the logical value 1.

recessive state

By definition, the recessive state will be overwritten by the dominant state.

recovery time

The time between the first bit of the error flag and the time point when the automatic retransmission can be started. In error active nodes, the maximum recovery time is 23 bit times, in error passive nodes it is 31 bit times.

redundant networks

In some safety-critical applications (e.g. maritime systems), redundant networks may be required that provide swapping capability in case of detected communication failures.

reference message

In TTCAN, the reference message starts each basic cycle.

remote frame

A message on the CAN bus with a particular bit set. The standard defines this message to mean a request for data, so the thought is that some node will see the remote frame and supply the requested data by sending an ordinary data frame.

remote frame (RF)

With an RF (only in Classical CAN) another node is requested to transmit the corresponding data frame identified by the same CAN-IO. RF's OLC has the value of the corresponding data frame OLC. RF's data field has a length of 0 byte.

remote request substitution (RRS)

In CAN FD frames, the RRS bit is transmitted at the position of the RTR bit in Classical CAN frames. It is transmitted dominantly, but receivers accept recessive and dominant RRS bits.

remote transmission request (RTR)

In Classical CAN, the bit in the arbitration field indicating if the frame is a remote frame (recessive value) or a data frame (dominant value).


Passive component that refreshes CAN bus signals. It is used to increase the maximum number of nodes, to achieve longer networks (>1 km) or to implement tree or meshed topologies.


A CAN controller is reset by a command (may be hard-wired). Before the CAN controller transits back to error active state, it has to detect 128 occurrences of the idle condition (11 consecutive recessive bit times) on the bus.

reset application

This NMT command resets all CANopen objects to default values or to the permanently stored configured values.

reset communication

This NMT command resets only the CANopen communication objects to the default values or to the permanently stored configured values. This NMT state is divided in sub-states waiting for node- 10, resetting and request boot-up.

re-synchronization jump width (SJW)

Number of time quanta with which the Phase_Seg 1 may be lengthened or the Phase_Seg 2 may be shortened.


See remote frame.

ringing suppression (RS)

The RS mechanism for CAN FD networks is introduced to minimize the ringing after bus-state changes on the CAN bus-lines, as the ringing limits the maximal possible data-phase bit-rate.

ringing suppression circuitry (RSC)

The RSC as specified in CiA 601-4 for CAN FD nodes comprises the bus-state change detection circuitry, the switch controller, and the differential internal resistance RRSC. If used, the RRSC is added to the bus-lines at a dominant­ to-recessive state change, changing the overall bus-line impedance. RRSC is switched-off after a defined time period. RSC can be implemented in the CAN transceiver, or connected to it as an external circuitry. It is recommended to locate RSCs on nodes with strong ringing, with long wire harness, or on nodes located far from the network termination.


See receive PDO.


See remote RRS substitution.


See remote transmission request.

Source CANdictionary (2016) - CiA CAN in Automation -