PBP Using too many instructions

[The Master]

The code i posted originally is what ive been using to test how many instruction cycles things take. I have 4 sockets (A to D) on this board each with 6 outputs (1 to 6).

'Define output pins
pA1 VAR PORTB.1
pA2 VAR PORTB.2
pA3 VAR PORTB.0
'etc...


'Then further down inside the TMR0 interrupt

'Is the vPWMPos equal to 0?
IF vPWMPos=0 THEN
	
	'Turn off any outputs that are less than 255
	IF vPWM[0]<255 THEN pA1=0
	IF vPWM[1]<255 THEN pA2=0
	IF vPWM[2]<255 THEN pA3=0
	'etc...
ELSE

	'If vPWMPos is less than any of the chanels then turn those chanels on
	IF vPWMPos=vPWM[0] THEN pA1=1
	IF vPWMPos=vPWM[1] THEN pA2=1
	IF vPWMPos=vPWM[2] THEN pA3=1
	'etc...
ENDIF

'Decrement the PWM counter
vPWMPos=vPWMPos-1

There doesnt have to be an array involved. I just used that to make other parts of the code a little easier. I could create a bunch of variables named vPWM0, vPWM1 etc instead. The important part is reducing the number of instructions an if statement uses or not using an if statement at all.

[Mike, K8LH]

Soft' PWM for that many outputs is difficult but you might be able to reduce 'overhead' using one of the following assembler methods;

Good luck on your project Sir. Regards, Mike

;
;  6 bit (single port), 256 step, 20 cycles (isochronous) for 16F
;
        movf    led+5,W         ; led[5] duty cycle, 0..255       |B0
        subwf   dcy,W           ; C = led[5] >= dcy               |B0
        rlf     shadow,F        ;                                 |B0
        movf    led+4,W         ; led[4] duty cycle, 0..255       |B0
        subwf   dcy,W           ; C = led[4] >= dcy               |B0
        rlf     shadow,F        ;                                 |B0
        movf    led+3,W         ; led[3] duty cycle, 0..255       |B0
        subwf   dcy,W           ; C = led[3] >= dcy               |B0
        rlf     shadow,F        ;                                 |B0
        movf    led+2,W         ; led[2] duty cycle, 0..255       |B0
        subwf   dcy,W           ; C = led[2] >= dcy               |B0
        rrf     shadow,F        ;                                 |B0
        movf    led+1,W         ; led[1] duty cycle, 0..255       |B0
        subwf   dcy,W           ; C = led[1] >= dcy               |B0
        rlf     shadow,F        ;                                 |B0
        movf    led+0,W         ; led[0] duty cycle, 0..255       |B0
        subwf   dcy,W           ; C = led[0] >= dcy               |B0
        rlf     shadow,F        ;                                 |B0
        xorlw   0xFF            ; for active hi outputs           |B0
        movwf   PORTB           ; update LEDs                     |B0
;
;  bump duty cycle counter
;
        movlw   b'00111111'     ; just in case                    |B0
        incf    dcy,F           ; bump duty cycle counter         |B0
        skpnz                   ; end-of-period? no, skip, else   |B0
        movwf   shadow          ; reset shadow                    |B0

;
;  6 bit (single port), 256 step, 15 cycles (isochronous) for 18F
;
        movf    dcy,W           ; duty cycle counter, 0..255      
        cpfsgt  Led+0           ; if(Led[0] >= dcy)               
        bcf     Shadow,0        ;   Shadow.0 = 0                  
        cpfsgt  Led+1           ; if(Led[1] >= dcy)               
        bcf     Shadow,1        ;   Shadow.1 = 0                  
        cpfsgt  Led+2           ;                                 
        bcf     Shadow,2        ;                                 
        cpfsgt  Led+3           ;                                 
        bcf     Shadow,3        ;                                 
        cpfsgt  Led+4           ;                                 
        bcf     Shadow,4        ;                                 
        cpfsgt  Led+5           ;                                 
        bcf     Shadow,5        ;                                 
        movff   Shadow,LATB     ;
;
;  bump duty cycle counter
;                         
        movlw   b'00111111'     ; just in case
        infsnz  dcy,F           ; if end-of-period                
        movwf   Shadow          ; reset shadow

[Jerson]

Very nice ASM coding

[The Master]

Ive been trying to get my head round this ASM code. Mike's ASM seems to do almost exactly what i want but i just want to clarify things as im completely new to ASM.

Is W some kind of temp byte? It appears that ASM compare commands only accept 1 input and that is always compared with W.

Ive read the part in the datasheet about CPFSGT. It says "Compare f with W, skip if f > W". I assume this means skip the following line of code

BCF looks pretty obvious. What is "Shadow" though? Is that a predefined variable of some kind or does it need declaring anywhere?

[Jerson]

Is W some kind of temp byte? It appears that ASM compare commands only accept 1 input and that is always compared with W.

Yes, W is the Accumulator on which almost all operations are performed.

What is "Shadow" though? Is that a predefined variable of some kind or does it need declaring anywhere?

Yes, shadow is a byte sized variable which holds a copy of the actual bits which turn on/off the leds attached to PORTB. It has to be declared like this

shadow:  var byte

[The Master]

So "LATB" is the ASM version of PORTB?

Is Shadow just a normal variable then? So i could call it LATBTemp if i wanted?

Is there a reason i would use Shadow instead of performing the operations directly on LATB?