Hello amer;

The CPU gives you access to a diagnostic buffer (CTRL + D in Step 7 Classic) that contains information on the events that catch the attention of the operating system. All alarms (including SF LEDs) will be logged there, and if possible the source of the problem will be identified.

Som,e of the messages will point to Missing OBs, with a specific number of OB requested. Simply create this OB (in Blocks), mane it with the requested number, (OB 83, OB86... OB122 are the numbers of diagnostic OBs) and download it to the CPU (without any internal programming). Next time the SF LED lights up the diagnostic buffer will be able to pinpoint the source of the problem with more details.

If you have problems understanding the diagnostic buffer cntents, please save oit ("As Text") and post the messgaes related to your problem here on the forum so we can help you out.

Hope this helps,

Daniel Chartier