Multiplexer address control..

[Mike, K8LH]

t'would be simpler/faster still if you were to use the B3..B0 pins as both the 'control' variable and 'control' I/O;

RES_VECT  CODE    0x0000            ; processor reset vector
    GOTO    START                   ; go to beginning of program
; TODO ADD INTERRUPTS HERE IF USED
MAIN_PROG CODE                      ; let linker place main program
START
 

        movlw   0x30            ; B7..B4 other I/O, B3..B0 = control
        movwf   LATB            ;
lopo
        incf    LATB,W          ; B3..B0 bits = control, 0..15
        xorwf   LATB,W          ; wreg = differences
        andlw   0x0F            ; ignore B7..B4 bits (and control mod 16 for free)
        xorwf   LATB,F          ; update B3..B0 bits, 0..15
 
        GOTO    lopo

[richard]

if I may...

Mike, K8LH

that's exactly what a good forum needs

your solution is excellent

[Mike, K8LH]

I like pedja089's solution which is probably about as simple, efficient, and elegant as you can get with pure PBP code. He might test clearing the four LATB bits and then setting them based on if control.0 = 1 then latb.4 = 1 (or something similar).

I have to say the code PBP generated for the "Control << 4" instruction was pretty dismal. I'm curious to see what XC8 will generate for that...

[richard]

I like pedja089's solution which is probably about as simple, efficient, and elegant as you can get with pure PBP code

it is simple but I wonder if it may cause some analog channel crosstalk effects when control inputs are changed sequentially like that esp at low clock speeds , just a thought.

[Mike, K8LH]

Oops! I didn't think of that...