Manual VIPA System 100V
Chapter 2 Decentral block periphery CAN-Bus CANopen
HB100E - SM-CAN - Rev. 15/02
2-3
CAN is based on a line topology. With the help of a router node, it is
possible to build-up a network structure. The number of participants per
network is only limited by the efficiency of the used bus driver module.
The maximum net extension is limited by the signal run times. At 1Mbaud,
for example, a net extension of 25m and at 50kBaud of 1000m is possible.
As transfer medium, CAN-Bus uses a screened 3core cable (5core
optional).
The CAN-Bus is working with voltage differences. Thus it is less sensitive
to interference than a voltage or current interface. The net should be
configured as line with a 120
Ω
terminating resistor at the end.
Your VIPA CAN-Bus coupler provides a 9pin plug. This plug allows you to
link-up the CAN-Bus coupler directly to the CAN-Bus net as slave.
All participants in the net are communicating with the same baudrate.
The bus structure allows the free installation or dismantling of station or the
start-up step by step. Later expansions don’t have any influence on stations
that are already integrated. The system realizes automatically if one partner
had a fail down or is new at the network.
Bus access methods are commonly divided into controlled (deterministic)
and uncontrolled (random) bus access systems.
CAN employs a Carrier-Sense Multiple Access (CSMA) method, i.e. all
stations have the same right to access the bus as long as the bus is not in
use (random bus access).
Data communications is message related, not station related. Every
message contains a unique identifier, which also defines the priority of the
message. At any instance only one station can occupy the bus for a
message.
CAN-Bus access control is performed by means of a collision-free, bit-
based arbitration algorithm. Collision-free means that the final winner of the
arbitration process does not have to repeat his message. The station with
the highest priority is selected automatically when more than one station
accesses the bus simultaneously. Any station that is has information to
send will delay the transmission if it detects that the bus is occupied.
For parameterization and configuration of the CANopen-Bus, the
manufacturers of the CANopen master deliver a software configuration tool.
This tool is able to access the object directory of your CAN slave and thus
parameterize the coupler.
The system specific properties of your CANopen couplers are delivered in
form of an EDS-file (
e
lectronic
d
ata
s
heet).
Transfer medium
Bus access
procedure
Parameterization
and configuration
