Technical data • Individual components
62
Automation PC 3100 user's manual V0.60
3.5.1.3.4 RS422 - Bus length and cable type
The RTS line must be switched on to switch the transmitter to active.
The maximum transfer rate of 115 kbit/s depends on the cable length as well as the type of cable being used.
Extension
Transfer rate
1200 m
Typ. 115 kbit/s
Table 64: RS422 - Bus length and transfer rate
The material used for the cable should have all of the following properties or deviate from them as little as possible
to achieve an optimal transfer rate.
RS422 cable
Property
Signal lines
Cable cross section
Wire insulation
Conductor resistance
Stranding
Shield
4x 0.25 mm² (24 AWG / 19), tinned copper stranded wire
PE
≤82 Ω/km
Wires stranded in pairs
Paired shield with aluminum foil
Ground line
Cable cross section
Wire insulation
Conductor resistance
1x 0.34 mm² (22 AWG / 19), tinned copper stranded wire
PE
≤59 Ω/km
Outer jacket
Material
Properties
Complete shielding
PUR compound
Halogen-free
Composed of tinned copper wires
Table 65: RS422 - Cable requirements
3.5.1.3.5 Operation as an RS485 interface
The pins of the RS422 default interface (1, 4, 6 and 9) must be used for operation. Pins must be connected as
shown.
RXD
RXD
TXD
TXD
9
6
4
1
DATA
DATA
Figure 11: RS232/422/485 interface - Operation in RS485 mode
The RTS line must be switched by the driver for each transmission or reception; there is no automatic switch-back
mechanism. This cannot be configured in Windows.
The voltage drop resulting from long cable lengths can result in greater potential differences between the bus
stations, which can hinder communication. This can be improved by running the ground wire with the others.
3.5.1.3.6 RS485 - Bus length and cable type
The maximum transfer rate of 115 kbit/s depends on the cable length as well as the type of cable being used.
Extension
Transfer rate
1200 m
Typ. 115 kbit/s
Table 66: RS485 - Bus length and transfer rate
The material used for the cable should have all of the following properties or deviate from them as little as possible
to achieve an optimal transfer rate.
