Specifications

The device remains offline until you repeat this procedure and send the Enable command.
Changing the Baud Rate of an Entire Bus
The following procedure represents recovery steps to synchronize the baud rate on the MS/TP bus. You may need
to perform this procedure if:
• the baud rate of the bus supervisor (typically, the NAE) does not match that of the bus
• you need to change the baud rate of the bus
• you connect two buses operating at different baud rates
In general, we recommend that you set the bus supervisor (NAE) to 38,400 baud and set all of the other devices on
the bus to Auto.
Note: To change the baud rate of the bus, you need a Wireless Commissioning Converter (MS-BTCVT-1), and you
need access to the Metasys system UI and the laptop where CCT and the Wireless Utility are installed.
Note: A TEC Thermostat Controller must not be the lowest numbered address on the bus.
To change the baud rate of a bus:
1. Connect the Wireless Commissioning Converter (MS-BTCVT-1) directly to the bus you want to change.
Important: This procedure disrupts bus communication until completed. Be sure you have connected the
Wireless Commissioning Converter to the correct bus before proceeding.
2. Start the Wireless Utility. (Refer to the Metasys CCT Bluetooth Technology Communication Commissioning
Guide [LIT-12011038] for more information on the Wireless Utility.)
3. In the Metasys system UI, change all of the devices whose baud rate is manually specified (that is, not set to
Auto) to the new baud rate.
Note: Change the baud rate of the bus supervisor last.
4. Change the baud rate of all bus repeaters, bus modems, and third-party devices to the new baud rate.
Note: Devices may appear to go offline as you change baud rates.
5. In the Wireless Utility, specify the new Baud Rate, select Force New Baud Rate, and click Change. This process
takes approximately 3 minutes.
Note: TEC Thermostat Controllers do not assume the new baud rate for 10 minutes.
6. Once the Force New Baud Rate process is complete, access the Metasys system UI and verify the baud rate
from the UI and that all devices came online.
Note: If the old baud rate is still the active baud rate, a device on the bus may still be manually set to use the
old baud rate.
Automatic Low Resources Monitoring
Resources such as available memory and internal queues are continually monitored by the BACnet® communications
software including the IP communications and MS/TP components of the controllers. If any resource becomes
overloaded, the BACnet communications software reduces the throughput (throttles it back) to allow the controller
a chance to recover.
Exceeded resources are classified into degrees of severity as follows:
• Warning means the resource is in short supply.
• Trouble means the resource may cause some observable problems.
• Alarm means the resource is causing observable problems.
• Critical means the resource is almost exhausted and operation may fail.
57MS/TP Communications Bus Technical Bulletin: Appendix: Maximizing and Troubleshooting the MS/TP Bus