Short summary

Name	`MB_GetState`
→POU type	→function
Category	more system blocks, blocks for Modbus, block with internal error diagnostic
Graphical interface
Available since	version 1.51.0 (for logi.CAD 3) and version 3.0.7 of the →runtime system This block is supported for →Raspberry Pi and for the platform `WindowsX86` (incl. the built-in PLC under Windows). version 1.109.0 (for logi.CAD 3) and version 3.19.0 of the →runtime system This block is supported for Raspberry Pi as well as for the platforms `WindowsX86` (incl. the built-in PLC under Windows) and `LinuxX86`.

Functionality

The block determines the state of a given →Modbus connection.

It is imperative that you are using MB_GetState in order to determine the state of a Modbus connection within each cycle of the application. Make sure that the application contains the required steps depending on the return code of MB_GetState. Do not use internal variables within the application for determining the state of a connection. – Please also observe the note on the usage as it is specified for the MB_InitTCP block.

Inputs, return value

Identifier

→Data type

Description

Inputs:

MBHandle

DINT

the handle for an existing connection (with initial value -1)

Return value:

–

SINT

returns the current state of the given connection handle:

0: invalid handle (not allocated)
1: connecting (during connection attempt)
2: connected
3: connection failed
4: connecting (before connection attempt)
5: invalid handle (closing connection)

Input EN and output ENO are available when →calling the block. See "Execution control: EN, ENO" for information on input EN and output ENO.

Internal error diagnostic for block

The block checks the following error cases: The LibModbus system service has not been loaded and/or you have no permissions to use Modbus (no enabled feature in the license for the →runtime system ).
In such an error case, the output ENO of the block is set to value FALSE (or an equivalent).

Example for usage within ST-editor

Best practice in order to get to know the usage of the Modbus blocks: Create a new project based on the project template Moving Light with Modbus Access and study this sample project. This project contains a usage of this block.