Canopen Baud Rate And Bit Timing - Beckhoff CX1500-M510 Manual

Canopen - bus interfaces for cx systems

Table of Contents

Product overview

Topology

CAN is based on a linear topology. The number of devices participating in each network is logically limited by

CANopen to 128, but physically the present generation of drivers allows up to 64 nodes in one network

segment. The maximum possible size of the network for any particular data rate is limited by the signal

transit time required on the bus medium. For 1 Mbaud, for instance, the network may extend 25 m, whereas

at 50 kbaud the network may reach up to 1000 m. At low data rates the size of the network can be increased

by repeaters, which also allow the construction of tree structures.

Bus access procedures

CAN utilizes the Carrier Sense Multiple Access (CSMA) procedure, i.e. all participating devices have the

same right of access to the bus and may access it as soon as it is free (multi-master bus access). The

exchange of messages is thus not device-oriented but message-oriented. This means that every message is

unambiguously marked with a prioritized identifier. In order to avoid collisions on the bus when messages

are sent by different devices, a bit-wise bus arbitration is carried out at the start of the data transmission. The

bus arbitration assigns bus bandwidth to the messages in the sequence of their priority. At the end of the

arbitration phase only one bus device occupies the bus, collisions are avoided and the bandwidth is optimally

exploited.

Configuration and parameterization

The TwinCAT System Manager allows all the CANopen parameters to be set conveniently. An "EDS" file (an

electronic data sheet) is available on the BECKHOFF website (http://www.beckhoff.com) for the

parameterization of BECKHOFF CANopen devices using configuration tools from other manufacturers.

Certification

The BECKHOFF CANopen devices have a powerful implementation of the protocol, and are certified by the

CAN in Automation Association (http://www.can-cia.org).

2.3.2