Post by thread:It never ends...

Ok... Remember that stupid BCD-to-Binary converter I posted about a month ago? Turns out that it has YET ANOTHER bug. This really shouldn't surprise me, I guess, since I wrote both previous versions while I was online and never even assembled or tested them. Normally, I wouldn't waste bandwidth endlessly reposting updated versions of a routine like this, but I've heard from a few foolhardy souls who tell me they're using it, so I feel a certain responsibility. Anyway, this new bug was discovered by Bob Fehrenbach; it manifests itself when THOU equals 0. Fortunately, the fix is pretty trivial; just add a "SKPZ" before the "DECF THOU", and add a "CLRC" after it. The newest version of the routine (which I STILL have neither assembled nor tested) follows: ; ; Four-Digit BCD to 2-Byte Binary Converter (version 3), ; written by Andy Warren. ; ; (C) 1995 Fast Forward Engineering. All right reserved. ; ; Permission is hereby granted for any non-commercial use, so long as ; this copyright notice remains intact. ; ; Version 1 - First try. Written at the ned of a 40-hour day. ; Version 2 - Got some sleep, found a bug in the "THOU = THOU*250/256" ; section, and fixed it. ; Version 3 - Fixed the "What if THOU = 0?" bug discovered by Bob Fehrenbach. ; THOU EQU [any register] HUND EQU [any register] TENS EQU [any register] ONES EQU [any register] TEMP EQU [any register] ; Enter with four-digit BCD value in THOU, HUND, TENS, and ONES. ; Exits with 16-bit result in THOU (hi-byte) and HUND (lo-byte); TENS, ; ONES, and TEMP are scrambled. BCD2BIN: CLRC ;------------------------ RLF TENS,W ;W = TENS*2. ; MOVWF TEMP ; ; By the way, this RLF TEMP,W ;W = TENS*4. ;-- is a pretty good ADDWF TENS ;TENS = TENS*5. ; 2-digit BCD to RLF TENS ;TENS = TENS*10. ; binary converter ADDWF ONES ;ONES = TENS*10 + ONES. ; by itself... ;------------------------ RLF THOU,W ;W = THOU*2 (CLRC not necessary here). ADDWF THOU,W ;W = THOU*3. MOVWF TEMP ; RLF TEMP,W ;W = THOU*6. CLRF TEMP ; SUBWF TEMP ; SKPZ ; DECF THOU ;THOU:TEMP = THOU*250 / 256. CLRC ; RLF TEMP ; RLF THOU ;THOU:TEMP = THOU*500 / 256. RLF TEMP ; RLF THOU ;THOU:TEMP = THOU*1000 / 256. RLF HUND,W ;W = HUND*2. ADDWF HUND,W ;W = HUND*3. MOVWF TENS ;TENS = HUND*3. RLF TENS ;TENS = HUND*6. RLF TENS ;TENS = HUND*12. RLF TENS,W ;W = HUND*24. ADDWF HUND ;HUND = HUND*25. CLRF TENS ; RLF HUND ; RLF TENS ;TENS:HUND = HUND*50. RLF HUND ; RLF TENS ;TENS:HUND = HUND*100. MOVF ONES,W ; ADDWF TEMP,W ; SKPNC ; INCF TENS ; ADDWF HUND ;HUND = LO-BYTE OF RESULT. SKPNC ; INCF TENS ; MOVF TENS,W ; ADDWF THOU ;THOU = HI-BYTE OF RESULT. DONE: ;THOU:HUND = 1000*THOU + 100*HUND ; + 10 * TENS + ONES. -Andy -- Andrew Warren - spam_OUTfastfwdTakeThisOuTix.netcom.com Fast Forward Engineering, Vista, California