SENDREG     EQU     0x20
BITCOUNT    EQU     0x21

#define     SDO     PORTB,0
#define     SCK     PORTB,1
#define     LAT     PORTB,2



SerOut      movwf       SENDREG     ;load data to be sent into sendreg
        movlw       0x08        ;init bit counter
        movwf       BITCOUNT
        bsf     SDO     ;default MSB=1
        btfss       SENDREG,7   ;does MSB=1?
        bcf     SDO     ;no, send 0
        bsf     SCK     ;pulse clock
        bcf     SCK
        rlf     SENDREG,F   ;shift bits
        decfsz      BITCOUNT,F  ;decrement bit counter
        goto        $-7     ;continue sending until bit counter = 0
        bsf     LAT     ;all 8 bits sent, pulse latch
        bcf     LAT     ;all lines low
        bcf     SCK
        bcf     SDO
        return              ;done