At 07:32 PM 1/19/98 +0100, you wrote:
>Hello EveryOne,
>
>I've written a piece of code... But unfortualy it doen not work right...
>The 16c84 communicates with 3 CD4094 IC's. (Serial to parrallel). The error
>MUST be in the hef4094 routine, but i can't finft the error... Who can find
>the problem?
>
>(-----Cut----)
>SendOne
>        bsf DATA
>        call wait
>        bsf CLOCK
>        call wait
>        bcf DATA
>        nop
>        bcf CLOCK
>        return
>
>SendZero
>        bcf CLOCK
>        call wait
>        bsf CLOCK
>        call wait
>        bcf CLOCK
>        return
>
>hef4094
>        movwf txbyte
>        movlw 0x07
>        movwf bitcount
>Sendbit
>        btfss txbyte, bitcount  ; Skip next line if bit is set.
>        call SendZero           ; Sends a 0
>        call SendOne            ; Sends a 1
>        decfsz bitcount,1       ; Decrement bitcount, SKip if Zero
>        goto Sendbit
>       return
>
>(----Cut-----)
>
>main
>        movlw 0xFF
>        call hef4094
>        movlw 0x00
>        call hef4094
>        movlw 0x00
>        call hef4094
>        goto main
>end
>
>This piece of code should make 8 of the 24 bits high... But when I look at
>the outputs of the CD4094 it isn't...
>He problably sends one Bit to much or something...
>Greetz,
>        Radboud Verberne.
>
Radbound,

I believe your biggest problem is trying to use a variable to select the
bit number. BTFSS needs a constant for the bit number so what it does is
use the address (probably truncated to 3 bits) of the variable <bitcount>.
Also, when you call SendZero, it returns and calls SendOne immediately.

You might try:

Sendbit
                rrf     txbyte,f        ;rotate LSB into carry bit
                btfss   STATUS,C        ;is it a 0
                 goto   Zero            ;yes, send a zero bit
                call    SendOne ;no, send a one bit
                goto    Nextbit ;go check bit counter
Zero            call    SendZero        ;go send a zero bit
Nextbit decfsz  bitcount,f      are we done?
                 goto   Sendbit
                return

I haven't tested this code or optimized it but it should work. Hope this
helps!

Greg Maki