0_Einstein,

They are all declared as inputs to FB1. These inputs are passed directly through to FB2 instances.

They are never written too, only read from.

Is that not legal?

Also this block has no outputs as the static variables are used inside the FB1 to control the connection and data transmission to an external server.

Hello,

In FB2, you use a timer with DB1 (That goes wrong)

Use a timer multi instance, see the following link:

How do you reduce the memory requirement using multi-instances?

Best regards,

Wizard

Wizard,

Ah right ok, I will change that. 

In the link you attached, if you then add another counter in the program, do you still use the same static variable IEC_Counter_0 or does it need to be different like IEC_Counter_1?

Hello,

When you use more timers in FB2, you should make another Static variable.

Best regards,

Wizard

Wizard,

Ok, so what should I do if I have multiple instance timers in other functions / function blocks?

Create a new data block for each block or just add more static variables and have one data block for all timer variables? 

DS_7

Can anybody provide some help regarding the initial question about the function blocks behaviour?

SUMMARY:
The TP timers are called twice in the duration of a PLC cycle. That causes one timer call interfering with the other. The answer is to use the multi-instance concept for the timers.

4) From the popup select: "Multi-instance"

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qwazee,

Thanks for your detailed answer. I know you were expanding on what Wizard had said but you both helped solve my problem, to which I am very grateful.

Wizard,

I didn't know you were pointing out the solution to my problem with the timers, I actually thought you had found an issue that was bad programming practice and that I should correct it. It wasn't until qwazee informed that you were in fact pointing out the error, so thank you for your help.

My problem has been solved.