CAN dictionary

Explains vocabulary and abbreviations used in CAN technology

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Definitions:

application profile

Application profiles define all communication object and application objects in all devices of a network.

application objects

Application objects are signals and parameters of the application program visible at the application layer API (application programming interface).

application layer

The application layer is the communica­tion entity of the OSI (Open System Interconnect) reference model. It pro­vides communication services to the application program.

acceptance filter

The acceptance filter in CAN controller chips is used to select messages that are received depending on the assigned identifier. Most of the CAN controller chips provide a hardware acceptance filter that filters CAN messages assigned with a specific identifier or a range of identifiers. The user-settable filter unburdens the micro-controller from the task of acceptance filtering.

acknowledge (ACK) delimiter

The second bit of the acknowledge field. It is by definition recessive. The dominant state of this bit is regarded as a form error and causes the transmission of an error frame.

acknowledge error

If the message-transmitting node detects the recessive state in the acknowledge slot, it regards that as acknowledge error condition. Acknowledge errors do not cause a bus-off condition. Normally they occur if the network consists of just one node and this node starts transmission of CAN messages.

acknowledge (ACK) field

The acknowledge field is made of two bits: acknowledge slot and delimiter.

acknowledge (ACK) slot

The first bit of the acknowledge field. It is transmitted recessively by the message­ sending node, and it is transmitted dominantly by all receivers, which have performed the CRC (cyclic redundancy check) successfully. If the message­ producing node detects this bit as dominant, it knows that there is at least one node that has received the message correctly.

active error flag

The active error flag is the first part of the active error frame made up of six consecutive dominant bits.

arbitration field

The arbitration field is made of the 11-bit or 29-bit identifier and the RTR bit (in CBFF and in CEFF) or the RRS bit (in FBFF and in FEFF). The arbitration field of the extended data frames (CEFF and FEFF) contains also the SRR (substitute remote request) and the IDE (identifier extension) bits.

arbitration phase

The arbitration phase indicates those parts of the CAN FD data frame that utilize the bit timing as specified for Classical CAN. The arbitration phase starts with the SOF and lasts till the sample point of the BRS (bit rate switch) bit. In addition, the final part of the CAN FD data frame, starting with the sample point of the CRC delimiter till EOF completes the arbitration phase. The inter-frame space is also transmitted with the arbitration bit time. During the arbitration phase the nomi-nal bit time is used.

Arinc 825-1

This specification by Aeronautical Radio (Arinc) defines a higher-layer protocol dedicated for in-aircraft networking. It is designed similarly to the CAN aero-space higher-layer protocol, however, it utilizes a 29-bit identifier. The physical layer is compliant to ISO 11898-2.

Arinc 826

This specification describes the down­ loading of software parts to line re­placeable units (LRUs). The specification is intended for avionic programmable devices.

assembly object

This DeviceNet object describes the content of the I/O message.

asynchronous PDO

Asynchronous PDO (process data object) is the historical term for event-driven PDO in CANopen.

attachment unit interface (AUI)

Interface between the physical coding sub-layer (PCS) as specified in ISO 11898-1:2015 and the physical medium attachment (PMA). PCS and PMA are sub-layers of the CAN physical layer.

automatic retransmission

Corrupted messages (data frames and remote frames) are retransmitted automatically after the error frames are successfully transmitted.

auto bit rate detection

In this mode, a CAN node listens only to the bus traffic, and when a valid message is detected, it acknowledges the received frame. If no valid message is detected, the CAN node switches automatically to the next pre-configured bit rate. There has to be one and only one node in the network that transmits messages. Many modern CAN controller chips support automatic bit rate detection. The same can be achieved by external circuitry.

AUI

See attachment unit interface.

Source CANdictionary (2016) - CiA CAN in Automation - www.can-cia.org