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• The network must be terminated at both ends with its characteristic impedance,
typically a 120 Ohm 1/4 W resistor.
• Maximum number of electrically connected CAN nodes is 64
• Maximum CAN cable length is 250 m (820 ft) and is derated depending on bit rates
and cable type.
• Stub connections off the main line should be avoided if possible or at least be kept as
short as possible. Stub connections must not have terminating resistors.
• To ensure a high degree of electromagnetic compatibility and surge protection the
cable should be twisted pairs and shielded. An additional cable conductor or pair may
be used for the CAN_GND reference.
Do not connect the cable shield to the CAN_GND pins or the connector shell! Use
an external chassis ground connection to terminate the shield.
The following diagram illustrates a typical interconnection between GCP-30 units and
the GCP-MG:
GCP-30
Figure 3.1: CAN bus topology
Wiring the RS-485 Modbus interface
The RS-485 Modbus interface is used for integrating the GCP-MG into a two-wire Modbus
over Serial Line network. The use of the RS-485 interface must be configured using the
web interface (See the section called "Configuring serial line Modbus"). The GCP-MG is
a Modbus slave device.
1
The number of logically adressable units may be less.
12
Termination
resistor
GCP-30
1
.
Shield
GCP-30
GND
CAN_H
CAN_L
GCP-MG
UMGCPMG-2201
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