BIFFI EHO, Installation, Operation And Maintenance Manual

Page: 38 / 92

February 2022
Installation, Operation and Maintenance Manual
VCIOM-15345-EN Rev. 1
34 Communication Protocols
Section 5: Communication Protocols
Figure 14 Modbus/Multi-drop Topology
5.1.2 Multi-drop Bus Topology
— Only one data path to each device from network master
— No short-circuit or ground fault protection in network
— Open-circuit protection only to the first cable fault
— No redundancy included
— Maximum network cable length is only 1200 m (4000 ft)
— Maximum number of valves in network is 32
— Repeaters required to extend the network
5.1.3 STC Terminal Connections
Table 6. STC Pin Connections
STC PIN Connections Modbus Connections
39 CHA +
40 Shield
41 CHA -
42 Shield
43 CHB +
44 CHB -
Primary Network
Master
RS-232, RS-485, or RS-422 Modbus
RS-485, Modbus, Twisted
Shielded-Pair Cable, 9600 Baud