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MICROCONTROLLERS MADE EASY

2.4 COMMUNICATION

CAN & J1850

CAN (Controller Area Network) is a multiplexed wiring scheme that was developed jointly by

BOSH and Intel for wiring in automobiles. J1850 is the SAE (Society of Automotive Engineers)

multiplexed automotive wiring standard that is currently in use in North America.

The CAN specification seems to be the one that is being used in industrial control both in

North American and Europe. With lower cost microcontrollers that support CAN, CAN has a

good potential to take off.

Figure 13. CAN Principle

I2C BUS - Inter-Integrated Circuit Bus (PHILIPS)

The I2C bus is a simple 2 wire serial interface developed by Philips. It was developed for 8 bit

applications and is widely used in consumer electronics, automotive and industrial applica-

tions. In addition to microcontrollers, several peripherals also exist that support the I2C bus.

The I2C bus is a two line, multi-master, multi-slave network interface with collision detection.

Up to 128 devices can exist on the network and they can be spread out over 10 meters. Each

node (microcontroller or peripheral) may initiate a message, and then transmit or receive data.

The two lines of the network consist of the serial data line and the serial clock line. Each node

on the network has a unique address which accompanies any message passed between

nodes. Since only 2 wires are needed, it is easy to interconnect a number of devices.

UART. A UART (Universal Asynchronous Receiver Transmitter) is a serial port adapter for

asynchronous serial communications.

USART. A USART (Universal Synchronous / Asynchronous Receiver Transmitter) is a serial

port adapter for either asynchronous or synchronous serial communications. Communications

using a USART are typically much faster (as much as 16 times) than with a UART.

VR02101L

GATEWAY

INTER

Motor

ABS / ASR

Dashboard

Fuse Box

COMFORT

Radio, Display

Navigation

BODY

Window, Lock

Seat, Lamps

Air Conditioner

FAST

SPEED

> 125 Kb / s

SYSTEM

SLOW

SPEED

< 125 Kb / s

SLOW

SPEED

System, Phone