Stack Under flow

[mister_e]

start:
'
'
'

LED1=0 '

main:
GoSub getkey

getkey:
kp1=0 'Clear kp1

after Main, should have a goto start or something like that

But i didn't get any error within MicroCode Studio using MPASM but get error with PM about WDTCON and LCDCON... in the PM M16F91X.inc file it miss those two lines

WDTCON		    equ     105h
LCDCON		    equ     107h

but shouldn't be the cause IMO

[Wayne]

Hi Steve
You only get the error if you use the MPLAB SIM tool or program the PIC
and install it in the board.


Thanks
Wayne

[mister_e]

So to be clear does

main:
GoSub getkey
Goto Start     ' <=== Add this line

getkey:
kp1=0 'Clear kp1

fix the problem... i guess yes !?!

[Wayne]

Hi Steve (MR. E)

Yes that did work and thank you very much for the help.
But one more thing WHY and what is a stack underflow?

Again Thanks

Wayne

[mister_e]

A short explanation:
once the program RETURN from GETKEY, it RETURN after the GOSUB line, then do once again the GETKEY sub, meet a RETURN without a previous gosub.

Gosub => stack+1 => stack = +
Return => stack-1 => stack = 0
Return +> stack-1 => stack=-1 <=== here's the underflow

[Wayne]

OK makes sence


Again Thanks for your help




Wayne