Hi, > Hello, I am fighting with 16f690 processor. I have two INT variables and > add them together. SDCC generates following code:
Annotated for clarity, low byte in [0], high byte in [1]: > ; .line 349; "main.c" gYfilter = gYfilter + gYrotation; > BANKSEL _gYrotation > MOVF _gYrotation,W ; W = gYrot[0] > BANKSEL _gYfilter > ADDWF _gYfilter,F ; gYfil[0] = gYfil[0] + gYrot[0] > BANKSEL _gYrotation > MOVF (_gYrotation + 1),W ; W = gYrot[1] > BTFSC STATUS,0 ; skip if no CARRY > INCF (_gYrotation + 1),W ; inc W to honor CARRY > BTFSC STATUS,2 ; skip if not ZERO > GOTO _00004_DS_ ; if W is zero, nothing to do > BANKSEL _gYfilter > ADDWF (_gYfilter + 1),F ; otherwise, gYfil[1]+=gYrot[1]+CY > > _00004_DS_: Looks good to me. > Is it correct ? if both low bytes are 0x00, first btfsc skips and the > second skips as well. so there will be no addition at all. The second BTFSC checks the ZERO flag, which is set iff `gYrotation[1]+CARRY == 0'. In this case, the high byte of gYfilter in fact does not require any change. Do you observe erroneous behaviour exactly when this code fragment is executed?!? What do you observe? What do you expect? Could you publish the failing/faulty source code? Best regards, Raphael ------------------------------------------------------------------------------ Open Source Business Conference (OSBC), March 24-25, 2009, San Francisco, CA -OSBC tackles the biggest issue in open source: Open Sourcing the Enterprise -Strategies to boost innovation and cut costs with open source participation -Receive a $600 discount off the registration fee with the source code: SFAD http://p.sf.net/sfu/XcvMzF8H _______________________________________________ Sdcc-user mailing list Sdcc-user@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/sdcc-user
