This document discusses the CAN bus protocol. It explains that CAN frames can transmit up to 1 Mbps over a maximum bus length of 40 meters. The data portion of each CAN frame can be up to 8 bytes, with the frame size variable between 0-8 bytes. The CAN bus uses a differential voltage logic over a twisted pair cable with 120 ohm terminating resistors to provide noise immunity and impedance matching.

1. Shyam Bhat
Vichara Vandana
Agenda
1) CAN Speed
2) CAN Data
3) CAN Bus
4) CAN Logic
5) CAN Controllers and Transceivers
6) CAN Network Topology

2. CAN frames ca go up to 1mbps speed with the bus length at max of 40 mts.
As the bus length increases above the maximum speed reduces.
In industry usually the CAN is configured at 500kbps speed
Lets say the baud rate is 500kbps  In 1 second, 500 *1000 bits can be transmitted
Lets say a single frame takes about 125 bits for example (without stuffing 111 bits)
So in a second the bus can fit around 2000 (500k /125) frames

3. frame
ECU 2
ECU 1
Application 1 Application 2
Data
Frame has 2 parts: PCI and Data
As per CAN protocol How much data can be sent in each frame?  8 Bytes
Is the data size variable?  Yes we can have 0 bytes or 1 byte or 2 bytes etc. Max is 8 bytes.
Is it possible to have data in bits?  No. Its in bytes. We cant have 2 bit or 27 bits etc its
always in bytes.

4. 120
ohm
Can High Can Low
 CAN bus is a Dual-Twisted pair wires called CanHigh and CanLow
 Differential Voltage Logic
 Logic1 = Recessive bit
 Logic0 = Dominant bit
 Why twisted pair?  Noise Immunity
 Terminated with 120 ohm resistor  Impedance matching
CAN_H CAN_L Delta V
Logic 1 2.5v 2.5v 0
Logic 0 3.5v 1.5v 2