CAN Controller Area Network BY-Ashutosh Bhardwaj Roll no. -1213231054 E.C-A
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.