B&R Automation PC 620, User Manual

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Technical data • Individual components
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189 Automation PC 620 with 945GME N270 CPU board User's Manual V 1.10
RS485 interface operation
The pins of the RS422 default interface (1,4,6 and 9) should be used for operation. The pins
should be connected as shown.
The RTS line must be switched each time the driver is sent and received; there is no automatic
switch back. This cannot be configured in Windows.
The voltage drop caused by long line lengths can lead to greater potential differences between
the bus stations, which can hinder communication. This can be improved by running ground wire
with the others.
The line ends of the RS485 interface should (at least for longer line lengths or larger transfer
rates) be closed. Normally a passive terminator can be used on the bus ends by connecting each
of the signal lines with 120
Ω
resistance.
RS485 - Bus length and cable type
The maximum transfer rate of 115 kBit/s depends on the cable type being used.
RS422 cable Property
Signal lines
Cable cross section
Wire insulation
Conductor resistance
Stranding
Shield 4 x 0.25 mm² (24AWG/19), tinned Cu wire
PE
≤
82
Ω
/ 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
PE
≤
59
Ω
/ km
Outer sheathing
Item
Characteristics
Entire shielding PUR mixture
Halogen free
From tinned cu wires
Table 95: RS422 - Cable requirements
Figure 77: Add-on RS232/422/485 interface - operated in RS485 mode
RXD
RXD
TXD
TXD
9
6
4
1
DATA
DATA