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7.4. MODBUS Network and
Daisy-Chaining
ACC
Control Link ACC Daisy Chain
Figure 7-12 -
Control Link ACC must be networked in a single
open communications loop, or daisy chain. A daisy
chain connects all the Control Link ACCs together in
a single unbranched series, and requires termination
jumpers to be set on the controllers at either end of the
chain. No branching or "star configurations" are
allowed.
7.4.1. Step 1: Disconnect Power to
the Control Link ACC and Open
the ACC Enclosure
WARNING! DISCONNECT THE SUPPLY
POWER FROM THE CONTROL LINK ACC
BEFORE OPENING THE ENCLOSURE.
OPENING THE ENCLOSURE WHILE THE
CONTROL LINK ACC IS POWERED MAY RESULT
IN ELECTROCUTION.
Connecting a Control Link ACC to a MODBUS
network requires you to remove the top cover from
the Control Link ACC enclosure. Press down the tab
at the main voltage end of the enclosure, and remove
front cover of the Control Link ACC. If the Control
Link ACC is already mounted in the case mullion,
you may have difficulty removing the front cover; if
so, loosen the top mounting screw before pressing the
tab.
16 • Control Link ACC I&O Manual
7.4.2. Step 2: Connect the MODBUS
Network Cable
ACC
Termination
+
Block
Figure 7-13 -
MODBUS network cable has two conductors plus
a shield. For each Control Link ACC, connect the two
conductors to the 485 terminals of the MODBUS
connector labeled + and - (at the bottom, low voltage
end of the enclosure), making sure to use the same
wire colors for each Control Link ACC connection.
For example, if the conductor wire colors are BLACK
and WHITE, use BLACK for all 485+ terminals and
WHITE for all 485- terminals (or vice-versa).
Connect the bare (SHIELD) wire to the center Shield
terminal (0V terminal on the E2).
7.4.3. Step 3: Set the Network
Address
NOTE: If you are networking Control Link
ACC only for purposes of sharing a dewpoint
sensor, you do not need to set a network
address. Set all network address dip switches or
jumpers to the DOWN (OFF) position. This will allow
the Control Link ACC to share a dewpoint sensor as
long as the network is physically present and terminated
correctly. The network address is only necessary for
assigning a network ID for MODBUS applications.
Depending on the hardware revision, the Control
Link ACC board has either eight dip switches or eight
three-pin jumpers, located in between the controller
and network status LEDs. Switches or jumpers 1-6 set
the network ID for the controller. Switches 7 and 8 set
the network baud rate and parity.
(bare wires) to 0V or
SHIELD terminal
Tie SHIELD to Earth Ground
at each node. Keep additional
wire length < (less than)
6" (15.24 cm)
Control Link ACC Network Connection
026-4704 Rev 6
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