MDK-ARM Keil, MDK-ARM Datasheet - Page 142

• Manufacturer Part Number: MDK-ARM
• Description: KIT REALVIEW MCU DEVELOPMENT
• Manufacturer: Keil
• Type: Compiler and IDEr

Specifications of MDK-ARM

• For Use With/related Products: ARM MCUs
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

142
Chapter 6. RL-CAN Introduction
The two most popular of these application layer standards are CANopen and
DeviceNet. The sole purpose of these standards is to provide interoperability
between different Original Equipment Manufacturers’ (OEM) equipment. If you
are developing your own closed system, then you do not need these application
layer protocols. You are free to implement your own proprietary protocol, which
many developers do.
CAN Node Design
A typical CAN node is shown in
the picture. Each node consists
of a microcontroller and a CAN
controller. The CAN controller
may be fabricated on the same
silicon as the microcontroller.
Alternatively, it may be a
standalone controller in a
separate chip from the
microcontroller. The CAN
controller is interfaced to the
twisted pair by a CAN
Transceiver. The twisted pair is
terminated at either end by a 120
Ohm resistor. The most
common mistake with a first
CAN network is to forget the
terminating resistors and then
nothing works.
The CAN controller has separate
transmit and receive paths to and
from the Physical Layer device.
This is an important feature of
the CAN node. Therefore, as the
node is writing to the bus, it is
also listening back. This is the basis of the message arbitration and it also
contributes to the error detection. The two logic levels, which are written on to
the twisted pair, are defined as follows; a logic one is represented by bus idle,
with both wires held half way between 0 and V
. A logic zero is represented by
CC
both wires being differentially driven.