Specifications

Table 5: Local FC Bus Rules
Rules/LimitsCategory
22 AWG Stranded, 3-Wire Twisted, Shielded Cable
Recommended Cable
2
The EOL switch must be set to On (or an EOL terminator installed) on the two devices located
at either end of each bus segment on an FC bus. The EOL switches must be set to Off (or
EOL termination disabled) for all other devices on the bus segment on an FC bus. See EOL
Termination on the Local FC Bus for more information.
EOL Termination
1 If third-party devices are connected to the bus, the cable lengths should be reduced (if necessary) to match the third-party
vendor recommendations.
2
The recommended cable type provides the best bus performance. See MS/TP Bus Cable Recommendations for information
on alternative cable types and lengths that may be used in MS/TP applications.
Figure 9: FC Bus with Three Bus Segments Connected with Repeaters
The bus segments on an FC bus are connected using repeaters (only). A repeater has two device connections,
which are independent of each other. Each device connection on the repeater is connected to a bus segment just
like any other device connection on the segment, and a repeater device connection can be connected at the end of
a bus segment or anywhere along the segment. When a repeater device connection is at the end of a bus segment,
EOL termination must be enabled on that repeater device connection. See Figure 10 for more examples of repeaters
on FC buses.
Table 6: FC Bus Specifications
SpecificationCategory
Message Headers checked using 8-bit Cyclic Redundancy Check (CRC) test.
Message data check using 16-bit CRC test.
Error Checking
0–255 (See Device Addresses on the MS/TP Bus for more information.)
Device Addressing
RS485Data Transmission Standard
BACnet® MS/TPSignaling Method
9600; 19,200; 38,400; or 76,800 baud as selected by bus supervisor. (See Baud
Rates on the MS/TP Bus.)
Signaling Rate
23MS/TP Communications Bus Technical Bulletin