Application Note
October 1995

Topic: Modbus Plus™ with TURCK sensoplex® 2
Product: MEB
Author: Scott Henson


This Application Note describes several methods for integrating a Modbus Plus device into a Square D system using the NR&D MEB module. SY/MAX® communication via the Square D 802.3 Ethernet, serial SY/MAX, and Net-to-Net applications are discussed.


The Turck sensoplex 2 system provides a high speed sensor network for a variety of applications including proximity sensors. Turck offers a Modbus Plus interface module (HS-MOD 03) to allow other Modbus Plus devices access to the sensor network data. The sensor data is available as normal Modbus Holding Registers in the 4xxxx range. The MEB module provides a convenient translation from various SY/MAX communication sources to the Modbus Plus network. Normal SY/MAX messages may be simply routed through the Modbus Plus port on the MEB as though it were another Net-to-Net connection. The MEB provides a bi-directional SY/MAX<>Modbus Plus protocol translation that is transparent to the source and end devices. Messages may come from any SY/MAX source; such as a Model 650 PLC's Ethernet Port, a Model 400 connected to a SY/MAX mode port on the MEB, or personal computer connected to a SY/NET "Blue Hose" via a Net-to-Net port on the MEB.

Turck HS-MOD 03 Configuration

The Turck HS-MOD 03 device provides a Modbus Plus interface that allows external Modbus Plus devices to access sensor data. Two Modbus Plus drop numbers are required to gain access to this data. The first drop number is the Modbus Plus Address of the HS-MOD 03. This number is determined by a series if DIP switches located inside the module. For these examples, the Turck device is set for Modbus Plus Address = 2. The Turck device requires a second drop number for the data path for the HS-MOD 03. In this example, only data path 1 is used.

Niobrara MEB Configuration

The Niobrara MEB has the following configuration for each of these examples:

Port Drop # Mode
E-Net 05 SY/MAX
Port 1 101 SY/MAX
Port 2 102 Net-to-Net
Modbus Plus 04

Both Port 1 and Port 2 are set for 9600 baud, EVEN parity, 8 data bits, and 1 stop bit. Port Driver Modes are both set for Point-to-Point for standard RS-422 operation. The Ethernet port is connected to the plant-wide network with other MEBs, EPE5s, Model 650s, Model 450, and personal computers with the SFI-610 interface. The Modbus Plus port is connected to the plant-wide Modbus Plus network with the HS-MOD 03, and other Modbus Plus devices such as Quantum PLCs, 984 PLCs, BM85s, and other Modbus Plus devices.

Ethernet Example

In this example, a Model 650 PLC requires sensor data from the Turck network for its normal operation. The Model 650 has a SY/NET Ethernet drop number of 01 and is connected to the same Ethernet network as the MEB. A simple TREAD message in the ladder code may be used to gain access to the data. It is just a matter of using the correct route.

In this case, a five drop route is required:

001, 005, 004, 002, 001

This first drop (001) is the Model 650's port, the second drop (005) is the E-net port on the MEB, the third drop (004) is the Modbus Plus port on the MEB, the fourth drop (002) is the Modbus Plus port number on the Turck device, and the last drop (001) is the path within the Turck device. The following rung may be used to read the first register of data in the Turck device and place that data in PLC register 1025.

SY/MAX Point to Point Example

Consider a Model 400 PLC with its COMM port 2 connected to Port 1 of the MEB. As stated before, MEB Port 1 is in SY/MAX mode with a SY/NET drop number of 101. The Model 400 may read the Turck data with a TREAD rung with the route:
101, 004, 002, 001

The first drop (101) is the MEB's Port 1, the second drop (004) is the Modbus Plus port on the MEB, the third drop (002) is the Modbus Plus port on the Turck device, and the last drop (001) is the path number for the Turck device. A typical communication rung is shown below:

SY/MAX Net-to-Net Example

A personal computer with an SFI-510 SY/LINK card is located on a "Blue Hose" SY/NET network. One of the CRM-510 NIMs on this network is connected to Port 2 of the MEB in Net-to-Net mode. The drop number of the Net-to-Net port is 102. The SY/LINK has a network drop number of 14. The route from the SY/LINK board to the Turck device is:
014, 102, 004, 002, 001

The first drop number (014) is the SY/LINK's computer port, the second drop (102) is the Net-to-Net drop on the NIM and MEB, the third drop (004) is the MEB's Modbus Plus port, the fourth drop (002) is the Turck's Modbus Plus port, and the last drop (001) is the path number within the Turck device.

Effective 01 October 1995 - Specifications subject to change without notice.

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