Specifications

8 UMMBRG300-1101
The Modbus RS-232 connector is a male 9-pin D-sub type located at the bottom side of
the mounted unit (refer to Figure2.1, “Location of connectors”). It has industry standard
EIA-574 data terminal equipment (DTE) pinout as shown in the following table and
picture:
GND
TDX
CTS
DTR
RI
RXD
RTS
1
6
CD
DSR
Pin Signal Function Direction
1 DCD (unused) in
2 RXD Receive data in
3 TXD Transmit data out
4 DTR (unused) out
5 GND Signal ground
6 DSR (unused) in
7 RTS (unused) out
8 CTS (unused) in
9 RI (unused) in
Table 3.2: Modbus RS-232 connector pinout
Maximum cable length is 15 m (50 ft) or a length equal to a line capacitance of 2500
pF, both at the maximum standard bit rate of 20 kbps. If operating at higher bit rates
the maximum cable length drops to 3 m (10 ft) at a bit rate of 57.6 kbps.
To assure a high degree of electromagnetic compatibility and surge protection the
RS-232 cable should shielded. The shield shall be connected to an external chassis
ground at the either or both ends, depending on the application.
The shield must not be connected to the GND pin.
To connect the MBRG-300 to a PC (Personal Computer) or any other device with
data terminal equipment (DTE) pinout you need a null-modem or cross-over cable.
Connecting Ethernet
The following table describes the 10BASE-T Ethernet RJ-45 connector pinout:
TX+
TX-
Pin Signal Function
1 TX+ Non-inverting transmit signal
2 TX- Inverting transmit signal
3 RX+ Non-inverting receive signal
4 Internal termination network
5 Internal termination network
6 RX- Inverting receive signal
7 Internal termination network
8 Internal termination network
Table 3.3: Ethernet connector pinout
We recommend to use Category 5 UTP network cable.