https://forge.codesys.com/forge/talk/CODESYS-V2/thread/082d3b471c/2020-02-27T21:39:37.659000ZRecent posts to Doubt about PLC_PRG...2020-02-27T21:39:37.659000Z2020-02-27T21:39:37.659000Zndzied1https://forge.codesys.com/u/ndzied1/https://forge.codesys.com9897a0af71322c1417def5f024557cc57cac94ee

<div class="markdown_content"><p>Hi speif,</p> <p>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.</p></div>

2020-02-27T21:39:33.350000Z2020-02-27T21:39:33.350000Zspfeifhttps://forge.codesys.com/u/spfeif/https://forge.codesys.comf7cfd2ed54752ec4158c4cdf9588092d1ad8c9ab

<div class="markdown_content"><p>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.</p></div>

2020-02-27T21:39:31.885000Z2020-02-27T21:39:31.885000Zndzied1https://forge.codesys.com/u/ndzied1/https://forge.codesys.coma995a40bccf5092f07da10fbf5ab27712a00dadf

<div class="markdown_content"><p>OK,</p> <p>If you would like to break up your project into logical elements then it would make sense to have more than one POU.</p> <p>Also, different programming languages are more suited to certain tasks than others.</p> <p>If you are controlling a lot of outputs with logic statements, then Ladder Diagram or Instruction List might make the most sense.</p> <p>If, on the same machine you need to do some math calculations then Structured Text should be considered.</p></div>

2020-02-27T21:39:27.738000Z2020-02-27T21:39:27.738000Zhcchinhttps://forge.codesys.com/u/hcchin/https://forge.codesys.com63d9506335929f163eadd1e9865c6fe376fdd57d

<div class="markdown_content"><p>my question is when do we need two PLC_Prg?</p></div>

2020-02-27T21:39:26.260000Z2020-02-27T21:39:26.260000Zndzied1https://forge.codesys.com/u/ndzied1/https://forge.codesys.com4c94c2fd198971a0279c3951b0bbf5c0e7f944bc

<div class="markdown_content"><p>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.</p></div>

2020-02-27T21:39:22.094000Z2020-02-27T21:39:22.094000Zhcchinhttps://forge.codesys.com/u/hcchin/https://forge.codesys.com2db1faf38ca212adcb03fb988081716e2ca5eda5

<div class="markdown_content"><p>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?</p> <p><img alt="IMG: PLC.JPG" rel="nofollow" src="https://forum.codesys.com//download/file.php?id=152"/></p></div>