Specifications
• Check for and correct unstable sensors.
• Reduce the number of devices on the bus, if possible.
• If running at less than 38.4k baud, increase the baud rate (if possible).
• Verify repeaters, if applicable.
- Verify that repeaters are used where needed.
- Verify that repeaters are configured and wired correctly.
- Verify that BACnet Routers are associated with a single integration (Remote Field Bus) at a single supervisory
device.
Reading the Baud Rate of Devices
Attributes in the Metasys system UI display the baud rate settings and current baud rates of devices on the bus.
Figure 27 shows an example of the baud rate attributes in the NCE.
If the NAE is connected to an MS/TP bus that is already communicating at an unknown baud rate, you can temporarily
set the NAE Field Bus Integration object Baud Rate Selection to Auto. You can then read the current baud rate from
the Active Baud Rate attribute in the NAE.
To read the baud rates of devices, see Table 21.
Table 21: Reading Baud Rates in the Metasys SMP User Interface
To Read the Baud Rate Setting and the Current Baud RateDevice
1. In the Metasys SMP UI, display the Field Bus integration.
2. Select the Hardware tab, Baud Rate Selection indicates the baud rate selection
specified for the NAE.
3. On the Diagnostics tab, Active Baud Rate displays the current baud rate of the
bus.
1
NAE
1. In the Metasys system UI, access the Field Bus integration.
2. On the Engineering Tab, expand the field device object. Double-click the desired
MS/TP bus object.
3. Baud Rate Selection indicates the baud rate selection specified for the field device.
Active Baud Rate displays the current baud rate of the bus.
1
Field Device on the FC Bus
2
1 This attribute displays the baud rate at which the device is currently communicating. If the device Baud Rate Selection is set
to Auto, you can use this attribute to see what the baud rate actually is.
2 This applies to Johnson Controls field controllers. Metasys system TEC Series thermostats and third-party devices may have
different means of reporting the baud rate.
55MS/TP Communications Bus Technical Bulletin: Appendix: Maximizing and Troubleshooting the MS/TP Bus