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The pin-assignment of CAN-bus connectors is shown in figure 8.
6.2 The CAN-Bus Standard
Developed in the 1980's, the CAN-bus norm had been established in the 1990's by the International
Standardization Organization (ISO) as a worldwide standard. Since then, CAN has become very
popular especially in automotive and industrial applications. CAN is cared for and further developed
by the CiA (CAN in Automation User Organization), an association of 300 well-known companies
engaged in different areas.
The CAN-Bus employs the so-called „Bus-Topology" as network topology; i.e. all participants on the
bus are connected via one single two-wire line (Twisted-Pair-cable, with or without shielding), which,
at its ends has to be terminated using 120 Ω bus termination plugs. Each appliance on the bus can
communicate with any other unit without restriction. Up to 100 network devices can be connected on a
single CAN-Bus.
Because the CAN-interfaces of all EVI Audio appliances is galvanically isolated from the rest of the
circuitry, network cabling also carries a common ground (CAN_GND), which guarantees that all
CAN-interfaces in the network are connected to the same ground potential. The ISOLATED /
GROUNDED switch in the UCC1 offers the possibility for switching the CAN-Ground (CAN_GND)
to circuitry ground potential. Normally, one UCC1's switch should be set to its GROUNDED-position
while all other UCC1s in the network should be set to ISOLATED.
BUS TERMINATION
120
Ω
The CAN-bus allows using different data rates. The actual data rate is indirect proportional to the bus
length. "Smaller" networks with short bus lengths permit higher baud rates of up to 500 kbaud. The
baud rate needs to be reduced (minimum 10 kbaud) in networks with extensive bus length. The
following table shows the relation between baud rate and bus length:
Fig. 8: CAN BUS IN / OUT connector pin-assignment
CAN
CAN
DEVICE
DEVICE
1
2
CAN_H
CAN_L
CAN_GND
Fig. 9: Bus-topology of the CAN-bus
CAN
DEVICE
n
CAN BUS UP TO 1000 m
24
BUS TERMINATION
120
Ω
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