BCD to Binary PIC18 assembly

Guys Having some issues with my bcd to Bin routines since I migrated to pic18.
I found that the binary value was 1 more than it should be.
The routine also started to freak out when large numers were use.

Anyone has a working pic18 routine around?

Problem solved. The statement to clear the status but before the rotations started
was missing.

 
 ;Enter with a BCD number in HUND, TENS, and ONES (one digit  
 ; per register).  Each register (well... TENS, anyway) must  
 ; hold a number in the range [0-9].  
 ;  
 ; Exits with ONES and HUND unchanged, TENS scrambled, and  
 ; HI_BYTE:LO_BYTE = (HUND * 100) + (TENS * 10) + ONES.  
 ;  
 ; This routine works for all BCD inputs in the range  
 ; [000-999].  
 ;  
 ; 29 cycles.  
 
 BCD2BINX:  
 
         
         bcf STATUS,C		
 
         rlcf    KEYTENS,W   
         SWAPF   KEYTENS   
         rrcf    KEYTENS   
         ADDWF   KEYTENS,W   
 
         ADDWF   KEYONES,W  
     
         BTFSC   KEYHUNDS,0  
         ADDLW   d'100'  
        
         CLRF    REFHIGH  
 
         BTFSC   KEYHUNDS,1  
         ADDLW   d'200'  
       
         rlcf     REFHIGH  
        
         BTFSC   KEYHUNDS,2  
         ADDLW   LOW (400)
 
          
         rlcf     REFHIGH 
          
         BTFSC   KEYHUNDS,3  
         ADDLW   LOW (800)  
 
      
         MOVWF   REFLOW  
 
         MOVLW   d'1'  
         
         ANDWF   REFHIGH,W  
         BTFSC   REFHIGH,1  
         ADDLW   d'1'  
         btfsc STATUS,C  
         ADDLW   d'1'  
 
         
         BTFSC   KEYHUNDS,2  
         ADDLW   HIGH (400)  
 
         BTFSC   KEYHUNDS,3  
         ADDLW   HIGH (800)  
 
       
         MOVWF   REFHIGH
 
        ; movlw d'1'
        ; subwf REFLOW
 
        ; btfss STATUS,C
        ; decf REFHIGH,F 
         
 
 		return
 
 
 
 
 

ORIGINAL: MBedder

Look at this one (should be 13 words/16 cycles ):

Actually that takes 15 words/16 cycles, because MOVFF is a double-word instruction.

Here's a modification that uses two less words/cycles.

        radix   dec
 bcd2bin:
        movf    tens,w
        mullw   10              ; PRODL = tens * 10
  
        movf    PRODL,w
        addwf   units,w
        movwf   bin_l           ; BIN_L = (tens * 10) + units
  
        movf    hundreds,w
        mullw   100             ; PROD = hundreds * 100
  
        movf    PRODL,w
        addwf   bin_l,f         ; BIN =  (hundreds * 100) + BIN_L
        movlw   0
        addwfc  PRODH,w
        movwf   bin_h           ;
        return

Even shorter:

 ;
 ; input : hundreds=0..9, tens=0..9, units=0..9
 ; output: PRODH:PRODL = 0..999.  No trashing.
 ;
 ; 10 words, 13 cycles (including call)
 ;
        radix   dec
 bcd2bin:
        movf    hundreds,w
        mullw   10              ; PROD = hundreds*10, 0..90
  
        movf    tens,w
        addwf   PRODL,w         ; 0..99
        mullw   10              ; PROD = [(hundreds*10) + tens]*10, 0..990
  
        movf    units,w         ; PROD = [(hundreds*10) + tens]*10 + units
        addwf   PRODL
        movlw   0
        addwfc  PRODH
        return

Good collaboration!

What would I do without you guys?


Great work. Good use of the harware multiplier.