Why the estimate period via simulator mismatches the acutal result?

[szwx0701]

I am developing code on MIN52LAN, When I simulated the execute time about a piece of code via IAR, I got cyclecounter =38 ，which means
about 1.6us in 22M Hz HIRC. But the actual result is 4us. Can someone tell me why?

[a_ziliu]

Please post your code. let me check it.