Strange behaviour of my PBP code.

[Fredrick]

Ok.. now I have tested with another PIC,a PIC16F887 and then it works, the "bug" is gone.
So why does it hang with a PIC18F2550, PIC184550, and 18F4520?

Does it have something with the config fuses to do? what have I missed?

[Darrel Taylor]

Hi Fredrick,

In the Check_Buttons subroutine, there's 2 Goto Main statements.

You should use RETURN to exit a subroutine.

Using GOTO will cause the stack to overflow.
With 18F's a stack overflow can cause a Reset.

But with 16F's the stack just wraps around and seems to work, although it's probably not working 100%.

[Fredrick]

Ohh so simple!

When I notified the problem fist time I was saying to myself that this time I will try to solve the problem without help from anybody, so I have spent a lot off hours on trying to find the problem, but then I give up and started a thread here again.

Thank you Darrel.

[Fredrick]

But it´s OK to use Goto´s within the subroutine as long as I call a label that is in the subroutine and only leave the subroutine by doing a Return

[Darrel Taylor]

Exactly!

You've got it now.
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[Fredrick]

How is it with variables?
If I overflow a byte sized counter it will turn to 0 after passing 255, but is it OK to let a variable overflow? or should I take care of the overflow like this

IF Counter > 254 Then 
Counter = 0
Endif

[Darrel Taylor]

For BYTE sized variables, when the value goes over 255 the upper bits are lost, which makes it automatically wrap around to 0.
You don't need to do it manually.

For words, it wraps when over 65535.
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