CANopen Fieldbus Topology TWIDO PLC

Firstly built up for the borne systems of automotive vehicle, the CAN communication bus is currently applied in a lot of areas, such as:
• building,
• industrial control,
• transport,
• devices of moving part,
• devices of medical.

The benefits of the system of CAN are:
• the allocation system of bus,
• reliability of data exchange,
• error detection.

Structure of master/slave
The bus of CAN has a structure of master/slave for bus management. The master controls
• communication errors,
• slave initialization,
• status of slave.

Communication of peer to peer
Communications on the bus are created peer to peer; at any time, every device can propel a request on the bus and the relevant devices respond. The requests circulating priority on the bus is decided by an identifier at each message level.

CAN identifiers
Open switches of CAN PDOs at link level utilize extensive identifiers more than 29 bits for CAN standard V2.0B. CAN standard V2.0A with 11 bit identifiers can only be applied for transmitting and receiving.

CANopen Fieldbus Topology
The architecture of CANopen a Twido system contains of:
• a compact base or modular base of Twido PLC,
• a master module of CANopen fieldbus or TWDNCO1M module installed on the expansion bus2 of Twido PLC’s,
• slave devices3,4 of CANopen.

NOTE:
1. The master module of TWDNCO1M CANopen is carried by the Twido base controllers.
2. Only single master module of TWDNCO1M CANopen can be installed on expansion bus of the Twido system.
3. The master module of TWDNCO1M CANopen can handle up to 16 CAN slave devices on a bus segment.
4. The CANopen fieldbus of TWDNCO1M does not support extensive addressing for slave devices of CAN.
The master of TWDNCO1M CANopen enables up to 16 devices of slave in the bus. The speed of transmission depends severely on the type of cable and the length of bus used. Baud Rate versus Cable Length will describes the relationship between the maximum transmission speed and the bus length (on a single CAN segment without repeater).

Cable Type and Impedance versus Baud Rate and Cable Length
The below table explains the correlation between the maximum speed of transmission for a given bus length in relative to the cable type used, cable gauge and impedance.
Maximum baud rate of transmission .......... Bus length
500 Kbit/s............................................. 100 m
250 Kbit/s............................................. 250 m
125 Kbit/s............................................. 500 m

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TWIDO PLC