Can Protocol Error Detection
Contents |
a sophisticated fault confinement mechanism. The CAN protocol is intended to be orthogonal, i.e. all nodes address faults in because of a protocol error detected at the client the same manner. Fault confinement is provided where each node constantly
Because Of A Protocol Error Detected At The Client Code 0x1104
monitors its performance with regard to successful and unsuccessful message transactions. A ?Transmit Error Counter? (TEC) and a because of a protocol error detected at the client (code 0x1204) ?Receive Error Counter? (REC) create a metric for communication quality based on historic performance. Each node will act on its own bus status based on its individual history. As
Because Of A Protocol Error Detected At The Client 1204
a result, a graceful degradation allows a node to disconnect itself from the bus i.e. stop transmitting. This means that a permanently faulty device will cease to be active on the bus (go into Bus Off state), but communications between other nodes can continue unhindered. If the bus media is severed, shorted or suffers from some other failure mode because of a protocol error detected at the client 1104 the ability to continue communications is dependent upon the condition and the physical interface used. Fault confinement is a checking mechanism that makes it possible to distinguish between short disturbances (e.g. switching noise from a nearby power cable couples into the transmission media) and permanent failures (e.g. a node is malfunctioning and disturbs the bus). Manipulation of the error counters is asymmetric. On a successful transmission, or reception, of a message, the respective error counter is decremented if it had not been at zero. In the case of a transmit or receive error the counters are incremented, but by a value greater than the value they would be decrement by following a successful message transaction. If a node detects a local error condition (e.g. due to local conducted noise, application software, etc.), its resulting error flag (primary error flag) will subsequently cause all other nodes to respond with an error flag too (secondary error flags). It is important that a distinction is made between the nodes that detected an error first and the nodes which
Metropolitan (MAN) Wide (WAN) Cloud (IAN) Internet Interplanetary Internet v t e A Controller Area Network (CAN bus) is a vehicle bus standard designed to allow microcontrollers and devices to communicate with each other in applications without a
Error Frame In Can Protocol
host computer. It is a message-based protocol, designed originally for multiplex electrical wiring within
Error Detection And Correction
automobiles, but is also used in many other contexts. Development of the CAN bus started in 1983 at Robert Bosch GmbH.[1] The error detection and correction techniques protocol was officially released in 1986 at the Society of Automotive Engineers (SAE) conference in Detroit, Michigan. The first CAN controller chips, produced by Intel and Philips, came on the market in 1987. The 1988 http://www.port.de/cgi-bin/CAN/CanFaqErrors BMW 8 Series was the first production vehicle to feature a CAN-based multiplex wiring system. Bosch published several versions of the CAN specification and the latest is CAN 2.0 published in 1991. This specification has two parts; part A is for the standard format with an 11-bit identifier, and part B is for the extended format with a 29-bit identifier. A CAN device that uses 11-bit identifiers is commonly called CAN 2.0A https://en.wikipedia.org/wiki/CAN_bus and a CAN device that uses 29-bit identifiers is commonly called CAN 2.0B. These standards are freely available from Bosch along with other specifications and white papers.[2] In 1993 the International Organization for Standardization (ISO) released the CAN standard ISO 11898 which was later restructured into two parts; ISO 11898-1 which covers the data link layer, and ISO 11898-2 which covers the CAN physical layer for high-speed CAN. ISO 11898-3 was released later and covers the CAN physical layer for low-speed, fault-tolerant CAN. Can in Automation (CIA) standard is used as the basis for the several major (7-layers) protocol development. The physical layer standards ISO 11898-2 and ISO 11898-3 are not part of the Bosch CAN 2.0 specification. These standards may be purchased from the ISO. [3] Bosch is still active in extending the CAN standards. In 2012 Bosch released CAN FD 1.0 or CAN with Flexible Data-Rate. This specification uses a different frame format that allows a different data length as well as optionally switching to a faster bit rate after the arbitration is decided. CAN FD is compatible with existing CAN 2.0 networks so new CAN FD devices can coexist on the same network with existing CAN devices. CAN bus is one of five protocols used in the on-board diagnostics (OBD)-II vehic
even blocking, an entire system, the CAN protocol implements a sophisticated fault confinement mechanism. The CAN http://www.can-wiki.info/doku.php?id=can_faq:can_faq_erors protocol is intended to be orthogonal, i.e. all nodes address faults in the same manner. Fault confinement is provided where each node constantly monitors its performance with regard to successful and unsuccessful message transactions. A Transmit Error Counter (TEC) and a Receive Error Counter (REC) create a metric for communication quality based on historic performance. Each protocol error node will act on its own bus status based on its individual history. As a result, a graceful degradation allows a node to disconnect itself from the bus i.e. stop transmitting. This means that a permanently faulty device will cease to be active on the bus (go into Bus Off state), but communications between other nodes can because of a continue unhindered. If the bus media is severed, shorted or suffers from some other failure mode the ability to continue communications is dependent upon the condition and the physical interface used. Fault confinement is a checking mechanism that makes it possible to distinguish between short disturbances (e.g. switching noise from a nearby power cable couples into the transmission media) and permanent failures (e.g. a node is malfunctioning and disturbs the bus). Manipulation of the error counters is asymmetric. On a successful transmission, or reception, of a message, the respective error counter is decremented if it had not been at zero. In the case of a transmit or receive error the counters are incremented, but by a value greater than the value they would be decrement by following a successful message transaction. If a node detects a local error condition (e.g. due to local conducted noise, application software, etc.), its resulting error flag (primary error flag) will subsequently cause all other nodes to respond with an error flag too (s