Modbus RTU HMI Connection Port

The HMI port on LTMT main unit with Modbus RTU protocol can also be used as an optional Modbus RTU communication port.

When the LTMT HMI port is used as Modbus RTU communication port:

LTMT main unit is connected to a Modbus RTU client in a point-to-point connection.
Modbus RTU client can be connected to the HMI port.
HMI port can be connected temporarily to a PC running the TeSys Tera DTM embedded in a FDT container for TeSys Tera system configuration.

The HMI port characteristics are:

Physical interface	RS 485 wire
Connector	RJ45

A Modbus RTU client can be connected to the HMI port on the front face of the LTMT main unit, as shown in the diagram below.

The table lists the Modbus RTU cables used for connection.

Designation	Length	Reference Number
Shielded cable for Modbus RTU bus, with two RJ45 connectors	0.3 m (1 ft)	–
	1 m (3.2 ft)	–
	3 m (9.8 ft)	–
Connection cable USB or RJ45	2.5 m (8.20 ft)	–

The LTMT main unit is connected to the Modbus RTU network with a shielded RJ45 connector in compliance with the following wiring:

Pin No.	Signal	Description
1	–	Not connected
2	–	Not connected
3	–	Not connected
4	D1 or D(B)	Transceiver terminal 1
5	D0 or D(A)	Transceiver terminal 0
6	–	Not connected
7	+5V	Auxiliary supply to HMI
8	0VL	Signal and power supply common

The LTMT HMI port has the following configurable settings:

NOTE: If LTMTCUF control operator unit is connected on HMI port, HMI port must be configured as follows:

The LTMT HMI port settings can be configured using the following interfaces:

A PC running the TeSys Tera DTM embedded in a FDT container, such as SoMove software.
A PLC or DCS via the communication protocol.