BACnet/IP Ethernet Network Topology for
CVE controllers
CVE controllers may be connected to a BACnet/IP building
automation network in multiple ways: as daisy-chained
devices, as part of a star (also called home run) type
network, or as part of a ring network.
To daisy-chain CVE controllers, connect the controllers
to the bus supervisor in a chain with the Ethernet cable
connecting to the CVE at the ETH-1 or ETH-2 port, and
connecting to the next device from the other port.
Benefits of daisy-chained networks are that they require
less physical wiring and new devices can be added easily
to the network.
In a star network, each CVE controller is connected
by Ethernet cable directly back to a main switch. This
configuration reduces the possibility of network failure
but requires more wiring to install.
A ring network is a chain of controllers virtually closed
by a software component in an Ethernet switch. Not
all switches support the ring topology. The dual-port
controller from Johnson Controls supports Media
Redundancy Protocol (MRP). With MRP, a ring of Ethernet
devices can overcome any single communication failure,
with a recovery time faster than a non-ring (daisy chain or
star) architecture.
For more information about network topologies for
Metasys BACnet/IP Controllers, refer to the
Metasys IP
Networks for BACnet/IP Controllers Configuration Technical
Bulletin (LIT-12012458)
.
FC Bus terminal block (or N2 protocol as
required) on CVM controllers
The FC Bus terminal block is a blue, removable, 4-pin
terminal block that fits into a board-mounted pin header.
When connecting the CVM to the FC Bus, wire the bus
terminal blocks on the controller and other FC Bus devices
in a daisy-chain configuration using 3-wire twisted,
shielded cable as shown in Figure 5. For more information
about FC Bus terminal functions, requirements, and
Figure 5: FC Bus terminal block wiring
Table 2: FC Bus configuration
Description
1
Wiring for a terminating device on the FC Bus
2
FC Bus terminal blocks
3
Wiring for a daisy-chained device on an FC Bus segment
4
Connects to the next device on the FC Bus
5
Isolated Shield connection terminal
Note:
The Shield terminal (SHD) on the FC Bus
terminal block is isolated and can be used to connect
the cable shields on the bus (Figure 5).
SA Bus terminal block
The SA Bus terminal block is an orange, removable, 4-
pin terminal block with +15 VDC that fits into a board-
mounted pin header.
When connecting an SA Bus device to the controller, wire
the SA Bus terminal block on the controller and other
SA Bus devices in a daisy-chain configuration using 4-
wire twisted, shielded cable as shown in Figure 6. For
more information about SA Bus terminal functions,
requirements, and ratings, see Table 7.
Figure 6: SA Bus terminal block wiring
Table 3: SA Bus configuration
Description
1
Wiring for a terminating device on SA Bus
2
SA Bus terminal blocks
3
Wiring for a daisy chained device on SA Bus
4
Cable shield connection
Note:
Connect the shields to ensure they are
continuous the entire length with only one ground
location.
5
Connects to the next device on the SA Bus
M4-CV Series VAV Box Controllers Installation Guide
5
