Table 34: TA5142-RS485(I)
Serial interface
Pin
Signal
1
A1
internally connected to A2
2
B1
internally connected to B2
3
GND
4
A2
internally connected to A1
5
B2
internally connected to B1
No.
Protocol
Description
1
Modbus
Modbus RTU, master or slave
2
CAA SerialCom
Support for blocks contained in the CAA_SerialCom.lib library
Bus line
Construction
2 cores, twisted, with common shield
Conductor cross section
> 0.22 mm
²
(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
.
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
The line ends of the bus segment must be equipped with bus terminating resistors. These
resistors are integrated in the module TA5142-RS485I. The pull-up and pull-down settings must
also be made on the circuit board of the module.
Protocols
Bus cable
Cable length
Bus termination
Device specifications
Processor modules > AC500-eCo
2022/01/31
3ADR010278, 3, en_US
79
