Handle TCP Modbus Arrays in C#

PLCnext Technology & PLCnext Controls
1

I use the Modbus TCP Server 4 (library Modbus TCP 7) and use the array arrModbusData also for another block.

In this block I read from the array and write to it. But I cannot access elements of the array as usual in C#. The data type of the array is MB_TCP_ARR_W_0_7167.
To my knowledge this corresponds to 16 bit → WORD in PLCNext and a ushort in C# The array ModBusData is defined for the other block in C# as follows
[InOut, DataType(“ANY”)]
public ushort ModBusData; The access with
ushort temp = ModBusData[0]
and writing with
ModBusData[1] = 0x0000
does not work and gives an error when writing the project.
The error messages are:
- Array boundaries out of valid range
- Runtime exception occurred on device How can this be done reading and writing to the ModBusData?

RegToken.PNG

2

Hello,

unfortunatly you can not connect arrays in the manner you are atempting.
Due to the nature of IECs static arrays getting C# and Eclr arrays to connect is a bit more complicated to setup.

Have a look here for one method:
https://github.com/PLCnext/CSharpExamples/blob/master/PLCnext_CSharpExamples/04_UserArray/UserArray.md
https://github.com/PLCnext/CSharpExamples/blob/master/PLCnext_CSharpExamples/04_UserArray/FBWithUserArray.cs The out of Bounds happens because IEC can not be directly cast to ushort You can however also pass by reference i will add a howto later.

Also just browse around a little at https://github.com/PLCnext/CSharpExamples/blob/master/PLCnext_CSharp
You can find many more usefull examples there. kind regards,
Oliver

3

Hello, Thanks a lot. My given array arrModbusData has the default data type MB_TCP_ARR_W_0_7167.

How can I use this data type as well in the new function block? It is still the same array as from the TCP Modbus