25
End Of Line (EOL) Resistors
MS/TP network must be properly terminated. For daisy chain configurations, you must install an EOL resistor at
each end of the daisy chain. Depending on your MSTP network configuration, the resistance value of the EOL
resistor may change:
•
Viconics’ devices are installed at both ends of the MSTP network:
120 Ohms resistor should be installed at each end.
•
A Viconics device is installed at one end of the MSTP network and a 3
rd
party device is installed at the
other end:
Install an End-Of-Line resistor value that matches the 3rd party devices instructions regarding its EOL
resistor value;
•
3
rd
party devices are installed at both ends of the MSTP network:
Follow the 3rd party devices instructions regarding its EOL resistor value.
Network Adapter
The polarity of the connection to the cable is important. From one module to the other it is important that the same
coloured wire be connected to “plus” or “+” and the other coloured wire be connected to the “minus” or ”-“. Figures
7 shows the proper MS/TP connections and the location of the Status LED. This Status LED may help to
troubleshoot network problems.
Figure 7: Correct MS/TP connections and location of a Status LED on a BACnet module
IMPORTANT NOTE:
The Ref terminal should
NEVER
be used to wire shields. The 2 shields from each feed of the
network connection to a controller should be wired together in the back of the controller and properly protected to
prevent any accidental connection to the ground.
The joined shield connection should then be grounded at a SINGLE point on the whole segment. More than one
ground connection to a shielded wire may induce ground loop noises and affect communication.
