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buffer to struct : position of variables


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I have following question :

I'm using modbus communication to read some values of a powermeter. Instead of reading 40 variables - one by one - I read them in one modbus cyle, into a buffer...

with the command buffer to struct, I can copy the values from the buffer to the struct. But when defining the structure, can I be 100% sure that the position of my variables in the structure is like I programmed the structure ?

I give an example :

I read 12 bytes via modbus ( 3 floating values) into buffer read[0..11]

I have a struct with variables float1 - float 2 - float 3

then I use buffer to struct....

are the first 4 bytes going to float1, second 4 bytes to float 2 and last 4 bytes to float3 ? I tested this, yes they do......but is this always like this?

I need to know if when recompiling the program, or copying this UDFB to another PLC program, will be always working with the "correct postioned" structure... 

 

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