using same pin for multiple purposes

[tasmod]

From the manual.

INPUT Make pin an input.
OUTPUT Make pin an output

Also PBP convention:-

MCB VAR PORTA.2

Symbol is Stamp compatibility, not that it really matters if you so wish.

You also have missing parameters in first lines for ADCON, TRIS etc either % or 0 or 1's

[Demon]

FOR MCB= 1 TO 0 STEP -1
PORTB=1
PORTC=1
MCB=MCB+1
NEXT

At first glance, this will run forever.

But, MCB is a bit; it can be 0 or 1. What happens first time through the loop when 1 is added to MCB when it is 1?

Robert

[Amoque]

In a loop (for/ next in this case) MCB will increment/ decrement by the step value automatically - no need to add or subtract the value. As:

For LP = 0 to -1 step -1
NOP
Next LP

LP will be set to 0 the first time through, "loop" and set the value of LP to -1, repeat the enclosed code, and then exit because the "to" condition (LP= -1) is met. Manipulating LP manually is not necessary and only bungs up the sequence. In the case where you subtract 1 from MCB: The initial loop starts with LP=0, in the code you reduce MCB to -1 (by subtracting 1), so the exit condition is met and the "loop" fails to repeat. NONE of the looping code is ever executed with LP equal to -1.