Overview

The following unconnected explicit messaging example shows you how to use the DATA_EXCH function block to read data from a remote device (for example, the STB NIP 2212 network interface module at IP address 192.168.1.6) using the Read_Holding_Registers service of the Modbus Object.

You can perform the same explicit messaging service using the EtherNet/IP Explicit Message window.

Implementing the DATA_EXCH Function Block

To implement the DATA_EXCH function block, you need to create and assign variables for the following blocks:

Declaring Variables

In this example, the following variables were defined. You can, of course, use different variable names in your explicit messaging configurations.

Configuring the Address Variable

The Address variable identifies the explicit message originating device (in this example, the Ethernet communication module) and the target device. Note that the Address variable does not include the Xway address elements {Network.Station} because we are not bridging through another PLC station. Use the ADDM function to convert the following character string to an address:

ADDM(‘0.1.0{192.168.1.6}UNC.CIP’), where:

• rack = 0

• module (slot number) = 1

• channel = 0

• remote device IP address = 192.168.1.6

• message type = unconnected

• protocol = CIP

Configuring the ActionType Variable

The ActionType variable identifies the function type for the DATA_EXCH function block:

Configuring the DataToSend Variable

The DataToSend variable identifies the type of explicit message and the CIP request:

Viewing the Response

Use a Control Expert Animation table to display the ReceivedData variable array. Note that the ReceivedData variable array consists of the entire data buffer.

To display the CIP response, follow these steps:

Step	Action
1	In Control Expert, select Tools → Project Browser to open the Project Browser.
2	In the Project Browser, select the Animation Tables folder, then click the right mouse button. A pop-up menu appears.
3	Select New Animation Table in the pop-up menu. A new animation table and its properties dialog both open.
4	In the Properties dialog, edit the following values:
	Name	Type in a table name. For this example: ReceivedData.
	Functional module	Accept the default <None>.
	Comment	(Optional) Type your comment here.
	Number of animated characters	Type in 49, representing the size of the data buffer in words.
5	The completed Properties dialog looks like this: Click OK to close the dialog.
6	In the animation table’s Name column, type in the name of the variable assigned to the RECP pin: ReceivedData and hit Enter. The animation table displays the ReceivedData variable.
7	Expand the ReceivedData variable to display its word array, where you can view the CIP response contained in the ReceivedData variable: Note: Each array entry presents 2 bytes of data in little endian format, where the least significant byte is stored in the smallest memory address. For example, ‘CE’ in word[0] is the lower byte, and ‘00’ is the upper byte.