CANController Area Network

BY-Ashutosh BhardwajRoll no. -1213231054

E.C-A

INTRODUCTION CAN bus is a vehicle bus standard designed to allow

microcontroller and devices to communicate with each

other in vehicle.

It is a message based protocol.

It is a multi-master serial bus

COMPARING WITH OTHER BUSESBus Trnsfer

typeTransfer rate(b/s)

Maximum Length(m)

Number of nodes

RS 232 Point to Point

20k 15 1

RS 425 Network 35k 1200 32

I2C Master slave

100k 1 128

SOI Master slave

110k 1 any

CAN Network 1M 40 2032

USB Master slave

480M 5 126

HISTORY Introduced by Robert Bosch in 1986 Developed for automotive applications Standardized in 1993 as ISO11898-1 CAN Standards

1. CAN 2.0A2. CAN 2.0B

CAN STANDARDS1. CAN 2.0A

Standard CAN (ISO 11898)11-bit Identifier1 Mbps

2. CAN 2.0BExtended CAN (ISO 11519)29-bit Identifier125 kbps

APPLICATIONS Automobiles Aerospace Maritime Industrial automachine Medical equipments

LAYERED STRUCTURE Application layer Object layer Transfer layer Physical layer

NETWORK COMPONENTS Physical Layer1. Cable.2. Connector 3. Transreciever

CAN Controller1. Part A2. Part B(Passive)3. Part B

Software

CABLES Twisted Pair Cables are used to get higher speeds. The Bit rate

of the data transformation is high for short distance and low for long distance.

Bus Length Bit Rate 40 Meters 1 Mbps 100 Meters 500 Kbps 200 Meters 250 Kbps 500 Meters 125Kbps 6 Meters 10Kbps

CAN CONTROLLERS Part A

11-bit Identifier Above 2000 devices in the Network

Part B Passive 11-bit Identifier

Tolerated 29-bit Identifier, but ignored Part B

29-bit Identifier Above 5 million devices in the Network

WORKING PRINCIPLE Uses CSMA/CD+AMP (Arbitration on Message Priority). Data messages transmitted from any node Using identifier all nodes will check whether the

message is intended for it or not The identifier determines the priority of the message Low bits are always dominant

FRAME TYPES Data Frame Remote Frame Error Frame Overload Frame

MESSAGE (DATA) FRAMEStandard Data Frame

Extended Data Frame

Start Of Frame:

Logic 0 indicates the beginning of a message frame. Arbitration Field:

11-bit identifier. Determines the priority of the message. Control Field:

6-bits. 2-bits are reserved for future use. 4-bit Data Length Code (DLC) indicates the number of bytes in the data field.

Data Field:

0 to 8 Bytes of data CRC Field:

15-bits Cyclic Redundancy Check Code and 1-bit delimiter Acknowledgement Field:

2-bits. Slot bit (1) overwritten by dominant bit from other nodes and delimiter bit (1).

End Of Frame Field:

7-bits (1111111). Indicates the End of the data frame.

Following the End Of Field is the Intermission field consisting of 3-bits (111) denotes the bus is recognized to be free.

REMOTE FRAME

The intended purpose of this frame is to ask for the transmission of the corresponding data frame. It is also used implement a type of request-response type of bus traffic management.

ERROR FRAME Consists of error flag (6-bits) and error delimiter (8-bits). Transmitted when a node detects a fault and will cause

all other nodes to detect a fault

OVERLOAD FRAME This frame is mentioned just for completeness of the

transaction.

ADVANTAGES

High throughput under light loads

Local and global prioritization possible

LIMITATION Unfair access - node with a high priority can "hog" the

network. Poor latency for low priority nodes.

CONCLUSION CAN is ideally suited in applications requiring a large

number of short messages with high reliability in rugged operating environments. Because CAN is message based and not address based, it is especially well suited when data is needed by more than one location and system-wide data consistency is mandatory.