How to check whether it is ZERO or not?

[Suraj143]

Hi I have a COUNT variable. When power up the PIC don’t know what value in it. (It depends on the last saved value in EEPROM)

I want to check whether it is ZERO or other. If it is zero I want to goto NORMAL program. If not zero I want to goto UPDATE routine.

Here is my code please tell me am I right?

	movf	COUNT,W		;get the count value
	xorlw	00h		;compare with zero
	btfss	STATUS,Z	;check the ZERO bit
	goto	UPDATE		;NO, it is not ZERO
	goto	NORMAL		;YES, it is ZERO

 

[blueroomelectronics]

Yep that'll work. MPASM also has a couple of macros built in to make that eaiser.

so..

  movf   COUNT,W   ;sets the z flag
  bz     NORMAL    ;it's zero so branch
  goto   UPDATE    ;not zero so goto UPDATE

PS movf will set the zero flag, you don't need the xor.

 

[Pommie]

Another useful way to test for zero is movf COUNT,F. This will set/clear the zero flag without corrupting W.

Mike.

 

[Suraj143]

Oh I see now I got it.Everywhere I'm corrupting W I must prevent this by moving the value to the FILE register.

Also built in macros really helpful.I must give a try for that.

Thank you both of you for the instant replies.