I don't think you "need" 2. It looks like you accidentally added another object and the default name is PLC_PRG but since, by default, there is one already there, you got a number appended to yours.
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Just to be clear do you understand the need of PLC_PRG? This is the main entry point of any CoDeSys application. It is synonymous to Main() in a C application. Without an entry point the CoDeSys application will generate a error. When would you ever need a PLC_PRG2? Well the point of a program is that it is a self contained object that has only one instance of that program in memory. Please ask more questions if still not clear or refer to "IEC61131-3: Programming Idustrial Automation Systems" book.
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By default, yes, PLC_PRG is the entry point. If your processor/installation of CoDeSys supports tasks then any POU can be made to run cyclicly so you don't necessarily need a PLC_PRG but it would be very confusing to have a main program with a different name as CoDeSys users are all used to the PLC_PRG convention.
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I have a doubt about PLC_PRG in the codesys sofware, why do need 2 PLC_PRG? what is the main function for the second PLC_PRG?
I don't think you "need" 2. It looks like you accidentally added another object and the default name is PLC_PRG but since, by default, there is one already there, you got a number appended to yours.
my question is when do we need two PLC_Prg?
OK,
If you would like to break up your project into logical elements then it would make sense to have more than one POU.
Also, different programming languages are more suited to certain tasks than others.
If you are controlling a lot of outputs with logic statements, then Ladder Diagram or Instruction List might make the most sense.
If, on the same machine you need to do some math calculations then Structured Text should be considered.
Just to be clear do you understand the need of PLC_PRG? This is the main entry point of any CoDeSys application. It is synonymous to Main() in a C application. Without an entry point the CoDeSys application will generate a error. When would you ever need a PLC_PRG2? Well the point of a program is that it is a self contained object that has only one instance of that program in memory. Please ask more questions if still not clear or refer to "IEC61131-3: Programming Idustrial Automation Systems" book.
Hi speif,
By default, yes, PLC_PRG is the entry point. If your processor/installation of CoDeSys supports tasks then any POU can be made to run cyclicly so you don't necessarily need a PLC_PRG but it would be very confusing to have a main program with a different name as CoDeSys users are all used to the PLC_PRG convention.