how to do case select in ASM??

[belinda_sg]

in c, we have if or case select to select different cases...

but how can we do it in assembly?

especially for the PIC programming?

can anyone give me some suggestion?
thx...

 

[Nigel Goodwin]

in c, we have if or case select to select different cases...

but how can we do it in assembly?

especially for the PIC programming?

can anyone give me some suggestion?
thx...

You do it with a series of subtractions and tests.

I'm presuming you are talking about the 4 bit A2D result you asked about in another thread, if so there's an easier and faster way to do it.

As you have only 16 possible results (with 4 bits) you could use a jump table. This works exactly like a lookup table, except instead of RETLW lines it uses GOTO's instead.

 

[kinjalgp]

Instead of subtraction, you can also use XOR function to test if variable = constant expression.

 

[motion]

Here's a PIC16 code sample:

; On entry, W reg contains the switch value
;
SWITCH:
	movwf	TEMP	; Save to a temporary register
;
	movlw	CASE1_VAL
	subwf	TEMP,W
	skpnz
	goto	CASE1
;
	movlw	CASE2_VAL
	subwf	TEMP,W
	skpnz
	goto	CASE2
;
	return
CASE1:
	return
CASE2:
	return