Specifications

Figure 6: EOL Terminations on an MS/TP Bus
Baud Rates on the MS/TP Bus
An MS/TP bus can be configured to communicate at one of four different baud rates. All of the devices on an MS/TP
bus must communicate at the same baud rate.
The baud rate setting determines the rate at which devices communicate data over the bus. The baud rate settings
available on Metasys MS/TP devices are 9600 bps, 19.2 kbps, 38.4 kbps, 76.8 kbps, and Auto. The baud rate setting
for Metasys devices is set in the Metasys software.
Note: The BACnet Standard only requires support for 9600 baud. Some 3rd party vendor devices might not support
all the baud rates supported by the Metasys system. Reducing the baud rate to accommodate these devices
affects overall performance.
We recommend setting all MS/TP bus supervisors (NAEs, NCEs, and BACnet Routers) to 38,400.
We recommend setting all field controllers on the FC bus or Remote Field Bus (FACs, FECs, VMA16s, and IOMs)
to Auto. In the Auto setting, the Metasys devices listen for the bus supervisor to communicate first; the devices then
automatically set their baud rate to the bus supervisor’s baud rate. FACs, FECs, VMA16s, and IOMs ship with a
default baud rate setting of Auto.
17MS/TP Communications Bus Technical Bulletin