I have declared 22 signal in real M blocks ,while my downloading time ,22 loop error is coming
You should fix the code loops !
Code loops occur when you read from and write to the same variable in the same program scan and the compiler cannot decide which should happen first. The compiler resolves this problem by simply executing your control modules in a "random" order.
This can lead to unpredictable results in some cases.
Only ever ignore code loops if you are sure you know why they have occured and that they will not affect the operation of your program. The most common reason for code loops is a programming error.
There is a setting in the options menu that allow you to download code even when loop errors are present. You cannot disable the warnings.