Schwank 40660000, Technical Manual

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10.6. Bus wiring
Each bus node must be assigned a unique address within the bus.
Line topology
Line topology must be used for the bus wiring. Stubs should always be avoided.
Modbus:

The maximum stub length per burner control unit is 0.5 m

Wiring diagrams can be found in the document "SchwankControl Electrical Installations"
CAN bus:

Stubs are not permissible. There are two clamping units per control unit for looping through the
bus [see illustration].
Clamping units must be either closed or connected!
The bus must either end at the clamping unit with a terminating resistor OR the wiring must lead to the
next node.
Bus termination
To terminate the buses, a 120 Ω terminating resistor between the data lines is required at both ends of
the bus wiring.
Modbus :

The control unit is equipped with a terminating resistor, i.e. the wiring must be carried out in such
a way that the line wiring ends at the control unit.
CAN bus:

The control unit is equipped with a terminating resistor, i.e. the wiring must be carried out in such
a way that the line wiring ends at the control unit.

If an operating unit is connected at both ends of the CAN bus, no additional terminating resistor
is required.
Figure 42: CAN-Bus control unit