CAN dictionary

Explains vocabulary and abbreviations used in CAN technology

Alphabetic selection:


padding sub-field

As defined in CiA 602-2, the sub-field of the data field containing meaningless bits in a fixed format in order to pad the data field to a defined byte limit.

parameter group (PG)

In J1939, ISO 11783, and ISO 11992, there are defined parameter groups, which specify the content of a specific CAN message.

parameter group number (PGN)

The parameter group number identifies uniquely the parameter group (PG). The PGN is mapped into the 29-bit identifier.

passive error flag

The passive error flag is the first part of the passive error frame made up of six consecutive recessive bits.


See physical coding sub-layer.


See process data object.

PDO mapping

In CANopen, in a PDO may be mapped up to 64 objects. The PDO mapping is described in the PDO mapping parameters.


See protocol data unit.

pending transmission request

There are one or more messages waiting for transmission in the CAN controller because the bus is not idle (node has lost arbitration).


See parameter group number.


See parameter group number.

phase segment 1 (Phase_Seg 1)

Part of the bit time used to compensate for edge phase errors. It may be lengthened by re-synchronization.

phase segment 2 (Phase_Seg 2)

Part of the bit time used to compensate for edge phase errors. It may be shortened by re-synchronization.

phase error

The phase error of an edge is given by the position of the edge relative to the sync segment. It is measured in time quanta.

physical coding sub­ layer (PCS)

Sub-layer of the physical layer. It receives from and sends to the transceiver circuitry the bit stream and performs the bit en-/ decoding, controls the bit timing and synchronization.

physical layer

Lowest layer in the OSI reference model defining the connectors, bus cables, and electrical or optical signals representing a bit value as well as synchronization and re-synchronization.

physical medium attachment (PMA)

Sub-layer of the physical layer. It specifies the functional circuitry for bus line transmission/reception and may provide means for failure detection. Here the physical signals are converted into logical signals and vice versa.

pin assignment

Definition of connector pins' usage.


See physical medium attachment.

pre-defined connection set

Set of CAN identifiers used as default values for different communication protocols in CANopen or DeviceNet.

pre-operational state

Part of the NMT slave state machine. In the NMT pre-operational state no CANopen PDO communication is allowed.


Attribute of a frame controlling its ranking during arbitration. In CAN data and remote frames (only in Classical CAN), the identifier (10) gives the priority. The lower the 10, the higher is the priority.

priority inversion

Priority inversion occurs if the lower prior object will be processed or communicated before the higher prior object. In not well­ designed CAN devices, there may occur inner or outer priority inversions.

process data

Application parameter that represents values from process interface inputs or values to the process interface outputs. Parameter in the CANopen object dictionary that can be mapped into PDOs.

process data object (PDO)

CANopen communication object defined by the PDO communication parameter and PDO mapping parameter objects. It is an unconfirmed communication service without protocol overhead. A PDO may contain up to 64 byte of data.


In CAN network a transmitter of messages is called a producer.

producer heartbeat time

In CANopen, the producer heartbeat time defines the transmission frequency of a heartbeat message.

propagation segment (Prop_Seg)

Part of the bit time used to compensate physical delay times within the network. These delay times consist of the signal propagation time on the bus line and the internal delay times in the nodes.


Formal set of conventions and rules for the exchange of information between nodes, including the specification of frame administration, frame transfer and physical layer.

protocol data unit (PDU)

As defined in CiA 602-2, PDU is the information exchanged between peer entities of an open system interconnection (OSI) layer implementation. This term is also used in AUTOSAR and other standards and specifications.

protocol exception event

Exception from the formal set of conventions or rules to be able to tolerate future new frame formats.

Source CANdictionary (2016) - CiA CAN in Automation -