All instructions related to OB33 (500ms) Stop working and no update value show on operator station

Ayman Elotaify

Dear Sir  I have problem I am using CPU S7-400 PCS 7 for Cement factory The programmer who made program divided instructions into three cyclic interrupt OB35 OB33 AND OB 38 My problem is all instructions related to OB33 (500ms) Stop working and no update value show on operatr station (Wincc) I did entire compileand download then it became ok After 1 month repeated My Question is what the reason behind this problem Note : Program was running smoothly since 11 years You may help me to resolve problem Regards

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Split from what happen when OB1 scanning and Cyclic Interrupt OB come ?.