Hardware Interface; Network Cable - Flowserve Limitorque MX Device Net Field Unit User Instructions

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Limitorque MX DeviceNet Field Unit FCD LMENIM2328-00 – 11/05

2.2.3 Hardware interface

The DeviceNet Limitorque Interface is comprised of a minimum of one PCB with two interfaces - One
for the DeviceNet Terminal Block connector and one for the SMT Main Board.
Figure 2.3 gives an overview about the hardware. The microcontroller on the DeviceNet Limitorque
Interface handles the DeviceNet protocol, stores the DeviceNet parameters in an EEPROM, and commu-
nicates with the SMT Main Board via SPI.
Figure 2.3 – DeviceNet Limitorque Interface

2.2.4 Network Cable

DeviceNet is a CAN - based protocol that uses 5 wires including a shield. Two of the conductors are
used for 24V DC power & up to 8 amps (4 amps for NEC Class 2) may be passed along the hi-way from
a suitable power source. Two conductors are used for the CAN bus signals, CAN_H and CAN_L, which
are usually smaller in diameter. Limitorque recommends Belden cable for connecting to a DeviceNet
network. The specifications for thick and thin cable (per site requirements) are as follows:
Table 2.2 – Belden Cable Specifications
AWG
Insulation
Belden (Stranding)
material
Part No. dia. Inches
(color code)
Nom. DCR
2 – 15 AWG
(19 x 28) Power pair
3.6 ohm/1000 ft (Black/Red)
11.8 ohm/km
3082A
2 – 18 AWG
(19 x 30) Data pair
6.9 ohm/1000 ft (Blue/White)
22.7 ohm/km
2 – 22 AWG
(19 x 34) Power pair
17.5 ohm/1000 ft (Black/Red)
57.4 ohm/km
3084A
2 – 18 AWG
(19 x 36) Data pair
28.0 ohm/1000 ft (Blue/White)
91.9 ohm/km
Nom
Nominal Nominal
Impedance
O.D. Capacitance
(ohms)
12.2 mm 120 12.0 pF/ft
7.2 mm 120 12.0 pF/ft
Test Maximum
Frequency Attenuation
(MHz) dB/100ft
0.125 0.13
0.5 0.25
1 1.36
0.125 0.29
0.5 0.50
1 1.70