7/25/2014 5:51 PM | |
Joined: 12/22/2006 Last visit: 1/25/2022 Posts: 1742 Rating: (308) |
Hello, AR stands for address register. The CPU has two of them (AR1 and AR2). For AR2, there is an FAQ explaining when the editor is using it: http://support.automation.siemens.com/WW/view/en/24519821 Because the system is using AR2, you must save it before you use it in your codeand restore it when youare done. For AR1, I don't now exactly when the system uses it, but I suspect the system to useAR1 when you access elements of an array. Therefore I apply the same save/restore rule for AR1, to avoid any unexpected behavior. In any case,the contentof AR1 and AR2 is not static. When you run into a block, you do not get the value back from previous cycle. In that aspect, you can consider that they behave like "temp" variables. Because temp variables are not static, you must initialise temp variables before you use them. This was also true in the past with Step7 V5.5. In TIA I detected thay you may even get warnings in the compilation info windowwhen you use a non initialized temp variable, which is a good thing. |
Best regards |
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