JVL MAC050 User Manual page 185

5.6 Expansion Mod. MAC00-FC2/FC4/FC41
5.6.4 CANopen® network
The CAN bus, is a serial bus with multi-master capabilities where different products from
different manufacturers can communicate with each other. This could be devices as
PLCs, motors, sensors and actuators. Message types have higher priority and are sent
first, for time critical applications. New devices can easily be integrated on a existing bus,
without the need to reconfigure the entire network. The devices are connected through
a 2 wire bus cable, and data is transmitted serially.
5.6.5 CANopen®, general information
CANopen® is a CAN-based higher level protocol. The purpose of CANopen® is to give
an under stable and unique behaviour on the CAN network. The CAN network is the
hardware level of the system, and CANopen® is the software level. CANopen® is based
on the communication profile described in CiA® DS-301, and it specifies all of the basic
communication mechanisms.
CiA® DS-301contains message types on the lowest software level. The DSP-402 CAN-
open® standard defines the device profile and the functional behaviour for servo drive
controllers, frequency inverters and stepper motor. The DSP-402 is a higher software
level, and it use the DS-301 communication, but is making the device independent of the
manufacturer. If the devices using only the DSP- 402 it is possible that some general data
can be lost.
The CAN bus with real-time capabilities work in accordance with the ISO11898 stand-
ard. The major performance features and characteristic of the CAN protocol are de-
scribed below:
Message-oriented protocol:
The CAN protocol does not exchange data by addressing the recipient of the message,
but rather mark each transmitted message with a message identifier. All nodes in the net-
work check the identifier when they receive a message to see whether it is relevant for
them, messages can there for, be accepted by none, one, several or all participants.
Prioritsation of messages:
As the identifier in a message also determines its priority for accessing the bus, it is pos-
sible to specify a correspondingly rapid bus access for messages according to their im-
portance. Especially important messages can thus gain access to the bus without a
prolonged wait-time, regardless of the loading on the bus at that moment.
This characteristic mean that especially important messages are transmitted with priority
even in exceptional situations, thereby ensuring proper functioning of a system even dur-
ing phases of restricted transmission capacity.
JVL A/S - User Manual - Integrated Servo Motors MAC050 - 4500
Terminator
CAN Node
master
CAN network
CAN_H
CAN Node
slave
CAN_L
Terminator
CAN Node
slave
TT1092GB
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