Concept
MS/TP Data and Shield Connections
The cable shield drain wire is connected to each MNB device to provide a ground reference to the isolated RS-485 interface in each of the MNB devices. This shield connection on each MNB device is not a local ground connection. The shield drain wire from the MS/TP bus cable must only connect to the specific terminal designated to receive the shield for the MS/TP bus. The terminal label/text reference varies a little in the device documentation between the MNB devices. In all cases, it will be a third screw terminal in a set of three on a terminal block identified for MS/TP communications.
The sequence of MSTP+, MSTP-, and Shield terminals are different from that presented in the generic MNB configuration diagrams. For more information, see MNB Configurations . Be sure to observe the signal name instructions for each of the specific products in their respective installation guides.
|
MNB Device |
Terminal Block Reference |
MSTP+ Terminal Number |
MSTP- Terminal Number |
Shield Terminal Number |
Shield Label Reference |
|
MNB-70 |
TB1 |
3 |
2 |
1 |
SHLD |
|
MNB-V1 / MNB-V2 |
TB1 |
3 |
2 |
1 |
SHLD |
|
MNB-300 |
P102 |
1 |
2 |
3 |
SLD |
|
MNB-1000 |
P103 |
1 |
2 |
3 |
SLD |
There are two shield connection terminals on the MNB-1000 device. Both are referenced as SLD in the product data. The terminal block identified as P102 (BACnet Network Communications) is the connection serving the MS/TP bus and only the SLD terminal on this terminal block should be used to connect the shield from the MS/TP cable. The other SLD terminal is adjacent on terminal block TB101 and is used only for separate I/O RS-485 Bus. This is also an isolated ground reference connection, but it is a different isolated ground from the MS/TP bus.
MNB BACnet Devices
MNB Configurations