AN887 Datasheet, PDF (9/12 Pages) STMicroelectronics – MICROCONTROLLERS MADE EASY

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
INTER
SYSTEM
Motor
ABS / ASR
Dashboard
Fuse Box
Air Conditioner
FAST
SPEED
> 125 Kb / s
GATEWAY
SLOW
SPEED
< 125 Kb / s
SLOW
SPEED
COMFORT
Radio, Display
Navigation
System, Phone
BODY
Window, Lock
Seat, Lamps
VR02101L
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.
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