Serial interface Pin Signal
1 A1
2 B1
3 NC (not connected)
4 A2
5 B2
No. Protocol Description
1 Modbus Modbus RTU, master or slave
2 CAA SerialCom Support for blocks contained in the CAA_SerialCom.lib library
Bus cable
Bus line
Construction 2 cores, twisted, with common shield
Conductor cross section > 0.22 mm² (24 AWG)
Twisting rate > 10 per meter (symmetrically twisted)
Core insulation Polyethylene (PE)
Resistance per core < 100 Ω/km
Characteristic impedance ca. 120 Ω (100 Ω...150 Ω)
Capacitance between the cores < 55 nF/km (if higher, the max. bus length must be reduced)
Terminating resistors 120 Ω ¼ W at both line ends
Remarks Commonly used telephone cables with PE insulation and a
core diameter of > 0.8 mm are usually sufficient.
Cables with PVC core insulation and core diameter of
0.8 mm can be used up to a length of approx. 250 m. In this
case, the bus terminating resistor is approx. 100 Ω.
Cable length
The maximum possible cable length of a serial connection subnet within a segment depends on
the transmission rate.
RS-485 for point-to-point or bus connection:
Parameter Value
Transmission rate 9.6 kbit/s to 115.2 kbit/s
Maximum cable length On request
Protocols
Option boards > TA5142-RS485 - RS-485 serial adapter non isolated option board
2021/06/29 3ADR010635, 2, en_US 135
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