DHW-UM-004
Val Controls A/S
•
Sallingsundvej 5
•
DK-6715 Esbjerg N
•
Tel. +45 7547 0600
•
www.valcontrols.com
Revision: 4
5/20
2.2
Modbus
Modbus
4
3
2
1
A
B
A
B
2.2.1
Terminals
Modbus 1 (A)
2 (B)
3 (A)
4 (B)
Terminals 1 and 3 are connected inside the device. Terminals 2 and 4 are connected inside the
device.
2.2.2
Electrical specifications
Modbus
Interface
RS485
Termination resistor
No internal resistor.
External resistor can be applied across terminal 3 and 4.
Termination resistors must have the value of 120 Ohm.
Galvanic isolated
A maximum of 247 nodes can be connected on the same daisy chain bus.
Typical shielding of the RS485 bus cable is done on the master side of the cable.
