B&R Industries Automation PC 620, User Manual

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Technical data • Individual components
Automation PC 620 User's Manual V 1.90
RS485 interface operation
In RS422 mode, the interface can also be operated as an RS485 interface. This is possible using
TriState switching, which is achieved using RTS (Request To Send).
Bus length and cable type RS485
The maximum transfer rate of 115 kBit/s depends on the cable type being used.
The material used for the cable should preferably have all or most of the following properties in
order to reach an optimal transfer rate.
Figure 68: Add-on RS232/422/485 interface - Operated in RS485 mode
Distance [m] Transfer rate [kBit/s]
1200 Type 115
Table 83: RS485 bus length and transfer rate
RS485 cable Property
Signal lines
Cable cross section
Wire insulation
Conductor resistance
Stranding
Shield 4 x 0.25 mm² (24AWG/19), tinned Cu wire
PU
≤
82 Ohm / km
Wires stranded in pairs
Paired shield with aluminum foil
Grounding line
Cable cross section
Wire insulation
Conductor resistance 1 x 0.34 mm² (22AWG/19), tinned Cu wire
PU
≤
59 Ohm / km
Outer sheathing
Material
Properties
Entire shielding PUR mixture
Halogen free
From tinned cu wires
Table 84: RS485 cable requirements