CANopen Programmer's Manual - Maccon.de

1: Introduction CANopen Programmer’s Manual
Example of a CANopen Move Sequence
CANopen master transmits a control word to initialize all devices.
Devices transmit messages indicating their status (in this example, all are operational).
CANopen master transmits a message instructing devices to perform homing operations.
Devices indicate that homing is complete.
CANopen master transmits messages instructing devices to enter position profile mode (pointto-point
motion mode) and issues first set of point-to-point move coordinates.
Devices execute their moves, using local position, velocity, and current loops, and then
transmit actual position information back to the network.
CANopen master issues next set of position coordinates.
Overview of the CAN Protocol
A Network for Distributed Control
The backbone of CANopen is CAN, a serial bus network originally designed by Robert Bosch
GmbH to coordinate multiple control systems in automobiles.
The CAN model lends itself to distributed control. Any device can broadcast messages on the
network. Each device receives all messages and uses filters to accept only the appropriate
messages. Thus, a single message can reach multiple nodes, reducing the number of messages
that need to be sent. This also greatly reduces bandwidth required for addressing, allowing
distributed control at real-time speeds across the entire system.
CAN Benefits
Other benefits of CAN include:
Wide use of CAN in automobiles and many other industries assures availability of inexpensive
hardware and continued support. Ready availability of standard components also reduces
system design effort.
CAN’s relative simplicity reduces training requirements.
By distributing control to devices, CAN eliminates the need for multiple wire connections
between devices and a central controller. Fewer connections enable increased reliability in
harsh operating conditions.
Device-based error checking and handling methods make CAN networks even more reliable.
Physical Layer
The physical layer of CAN is a differentially driven, two-wire bus, terminated by 124-Ohm resistors
at each end. The maximum bit rate supported by CAN is 1,000,000 bits/second for up to 25
meters. Lower bit rates may be used for longer network lengths.
14 Copley Controls