Section 50
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6
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Communications
Physical Layer:
The MX4 module features one asynchronous RS232 serial communication
port, one asynchronous RS485 serial communication port, and one CANBUS 2.0B proprietary
communication port.
RS232 Interconnect:
The module is equipped with screw terminals called Port 1. This
connection is typically used to poll the information for a specific module using twisted shielded
pair cable suitable for RS232 networks. The simplest form of these networks are 3-wire, half-
duplex, using RX, TX and GND terminals. The TX terminal is the “TRANSMIT DATA” signal,
the RX terminal is the “RECEIVE DATA” signal, and the GND is the “COMMON GROUND”
signal for the communication line. These signal lines will take turns transmitting and receiving
depending on the device using the RS232 network at any given instant. The MX4 also
provides connections for CTS and DTR signals if required for 5 wire RS232 connections.
RS485 Interconnect:
The module is equipped with screw terminals called Port 2. This
connection is typically used to poll the information for a specific module using twisted shielded
pair cable with 120 ohm impedance suitable for RS485 networks. These networks are 2-wire,
half-duplex, and feature an “A” terminal 49, “B” terminal 50, and “SHD” shielded ground
connection. The A terminal is the + or non-inverting signal, and the B terminal is the – or
inverting signal. These signal lines will take turns transmitting and receiving depending on the
device using the RS485 network at any given instant.
Baud Rate:
9600 fixed (RS232/RS485)
Protocol:
Modbus RTU. This is a binary communication protocol. All data will be contained in
unsigned 16-bit Modbus Holding Registers (addressed starting at 40001). Following the
Modbus RTU specification, the Most Significant Byte in a 16-bit word is broadcast first,
followed by the Least Significant Byte.
Refer to the Modbus RTU map provided in this manual for a detailed mapping of the available
data and data scaling.
CANBUS 2.0 B Interconnect:
The module is equipped with screw terminals called Port 3.
This connection is typically used to provide the interconnections between the main control
module which polls the information for a specific module using twisted shielded pair cable with
120 ohm impedance suitable for CAN networks. This network protocol is proprietary
CANBUS, and features a “HI”(CAN H) terminal 52, “LO”(CAN L) terminal 53 connection, and
“SHD” shielded ground connection.
