S7-315 FC Timers

I have an FC that I call in 18 different instances. I need to add a timer to the FC now. It appears as though if I just enter a timer, say T10, then this timer follows through for each instance and of course causes a problem since I need it to be individualized. Is there a way to make the Timer a "variable" with the interface menu?

Thank you.

What is an "FC"?

Well, you could declare a timer as an In/Out variable to the function. That way each instance would have its own timer.

Lancie, an FC is a Function Call in the Siemens S7 world. It's basically a function with associated static data like a Function Block would have.

Thank you. I just "discovered" that and have already tested. Seems to work good. I simply select "out" rather than "in/out" is this OK?

Also since I'm here...

I now have to add 4 timers per FC. Isn't there a way to have this done internally within the function so that I do not need external inputs for the timers? Perhaps it would need to be an FB?

Newbie to S7.

Thanks again.

Sure, you can do just about anything. One of my projects uses over 300 timers, and I don't explicity declare any of them. But if you are a newbie, I wouldn't go down that road right now. But just to give you something to think about, you can address timers indirectly.

For instance, if you passed in an int called something like "TimerInstance" and entered "10", you could point to the timer indirectly like this:

A T[#TimerInstance]

If you needed, say, five timers in this function, you wouold just have to increment TimerInstance:

L #TimerInstance
+ 1
T #TimerInstance

A T[TimerInstance]

You would now be pointing to Timer 11, and so on.

Daynada said:

I now have to add 4 timers per FC. Isn't there a way to have this done internally within the function so that I do not need external inputs for the timers? Perhaps it would need to be an FB?

Click to expand...

Yes, convert to a function block and use the IEC timers SFB4/5 - you can then have as many as you like in each function block without having to worry about timer numbers.

This post explains how to embed FBs within another FB. This is called multiple instance.
http://www.plctalk.net/qanda/showpost.php?p=50741&postcount=16
If you add the IEC timers (SFBs) in the same way as in the example, then you do not have to worry about assigning the timers for each time you call the FB with the embedded IEC timers. They get assigned automatically to the instance DB of the calling FB.

edit: Actually, the example shows double multiple instance (an SBF, within an FB, within an FB). I dont hope that confuses you

I personally like using Multi-Instance FB but seeing as your new to Step 7 you could use FC80 Timer located in TI-S7 Library. You'll find the SCAN time is published by CPU in OB1. Move that to Global memory area and pass scan time into FC80...it will do the rest.

You'll need to pass in work memory for status but this will allow you to call FC80 for each timer you need in your block.

Nick