DL7, DL7L
37
6.3 Wiring diagrams for module M
6.3.1 Connection of RS-485 data transmission line
Fig. 6.21 Wiring diagram for RS-485.
Notes:
The device RS-485 receiver/driver allows connection of up to 32 devices.
An RS485-MODBUS configuration must have one trunk cable, along which devices are
connected, directly (daisy chaining) or by short derivation cables.
The maximum bus length depends on the baud rate, the cable (gauge, capacitance or
characteristic impedance), the number of loads on the daisy chain. For a 9600 Baud Rate
and 0.125 mm
2
(AWG26) or wider gauge, the maximum length is 1200 m. The derivations
must be short, never more than 20 m.
To minimize the reflections from the end of the RS-485 cable it is required to place a line
termination near each of the 2 ends of the bus. The device has an internal termination
system, activated by DIP switch on the left side of the terminal block. The correct operation
of the terminator requires setting both switches in the same position.
The ‘common’ wire should be used for all RS-485 ports. For the device as a common
signal the
power supply ‘-’ (terminal no. 6) or functional ground (terminal no. 7) have to be
used.
6.3.2 Ethernet port
Ethernet (100Base-T) port is located in the rear panel of the device. Outputs connections
are compliant with EIA/TIA-568A/B. A LAN cable (Patch Cord) ended with
RJ-45 plug may be connected to this port.
