Technical data

Wiring Types ECT MODBUS Networking to E2s • 39
that has the latest version of firmware on it.
22.4.Wiring Types
Emerson Retail Solutions specifies Belden #8761
shielded twisted pair cables for use as MODBUS wir-
ing (or Belden #82761 and Belden #88761 for plenum
installations).
For MODBUS network wiring of XR670K -
XR679K controllers to E2, Belden #8641 (CPC P/N
135-8641) is the recommended wire type to use.
If the recommended cable is not available in your
area, be sure the wiring meets or exceeds the follow-
ing specs:
22.5.MODBUS Termination
Blocks
Because the XR670K/XR679K device has no on-
board means of termination, use the MODBUS termi-
nation block (P/N 535-2711) for termination that can
be wired to the end of the cable segment using the
three-pin connector. Wire the two signal wires to the
outside terminals, and connect the shield to pin 18 of
the device, keeping the exposed shield wire length as
short as possible (3 inches ideal maximum length).
Figure 22-9 - Network Summary Screen
Shielded? Yes
Conductor Type Twisted Pair
Gauge 18 - 24 AWG
Capacitance between
signal wires
31 pF/ft or less
(9.45 m) or less
Capacitance between
signal and shield
59 pF/ft or less
(17.98 m) or less
Maximum Length
4000 ft/18 to 22 AWG
(1219.2 m)
2500 ft/24 AWG
(762 m)
Nominal Impedance 120W±50W
Figure 22-10 - MODBUS Termination Block (P/N 535-2711)
FROM LAST
DEVICE
AT END OF
DAISY-CHAIN
SHIELD WIRE
(CONNECT TO
OF DEVICE)
PIN 38
TO TERMINAL DEVICE