Hi,

I have Uncertainties about early part of this RAMP function programming. 

Mohammad Razmjoo

 I tracked RLO and STA by HOLD mode and MONITORING and it seems to be jumping always but the result of the program is correct too.

Mohammad Razmjoo

#flag1 is a bool temp and it used as a trick to execute one time!!

And therein lies the problem as TEMP variables are only valid while the FC/FB is executed.

Next time the FC/FB is called, TEMP variables can have any value in them (presuming this code runs in an S7-300 or 400 as its seems to be the case here).

As such the golden rule for usage of TEMP variables is: Always unconditionally write to them before you read from them.

If you need to memories values between each FC call, use IN_OUT's (or better still, use an FB and STAT's if it is a fair number of variables whose values need to be memorised) 

Oh thanks a lot for your advices and tips.

So that is why I couldn't monitor that instruction group?! And you are agree about that those instruction group execute just one time?

Hello Mohammad;

The only way to ensure that your instructions are only executed once when your block is executed  is to use the FP instruction (in STL), to program a positive edge detection. Once the positive edge has been used, it will not execute again unless you change the bit you have selected for the FP.

If you intend to program in STL I should suggest you save and study this manual, it will save you many headaches.

https://support.industry.siemens.com/cs/ww/en/view/109751814

What our friend fritz was trying to tell you when he used the term "unconditionnaly" was it is imperative that before you read any TEMP value (variables marked with "#")  that you write an initial value to them, since when you open your present function they still carry the temp values from the last opened block: all your blocks share the same local stack. You cannot predict what these temp values will be when you call your block, so you must start by placing initial values in each one when you open the function.

Please read fritz' last paragraph and try to understand (and apply) his suggestions.

Hope this helps,

Daniel Chartier

dchartier

Hello Mohammad;

The only way to ensure that your instructions are only executed once when your block is executed  is to use the FP instruction (in STL), to program a positive edge detection. Once the positive edge has been used, it will not execute again unless you change the bit you have selected for the FP.

 Ahhhhh!  That simple point!! Thanks very much friend. you are an angel !!

Even in Monitoring and HOLD mode is clear now!!