Post by thread:[PICLIST] [PIC] bsf, FSR?

----- Original Message ----- From: "David Queen" <spam_OUTdaqueTakeThisOuTSWBELL.NET> To: <.....PICLISTKILLspam@spam@MITVMA.MIT.EDU> Sent: Tuesday, May 08, 2001 9:25 PM Subject: [PIC] bsf, FSR? > Is there a way to use bit functions with the FSR or another way to select > which bit with a value you can update in a loop? I have done this, though its probably not the most efficient way. However, if someone knows of a more efficient(code space) way please let me know, as this lacks finesse. This routine(Store_Bit) is called with rombit_idx containing the one-relative (1,2,3..64) bit number to be set or cleared. bits.1 contains the value to be stored(0,1). Be careful of page boundarys. <Warning - untested as of yet (this is for a Dallas one-wire search, but I dont have any 1-wire devices yet)> Store_Bit call SetupFSR ;convert rombit_idx to something we can use ;Determine if we need to set a bit (1) or clear a bit (0) rrf bits, W ;get bit.1 value right justified into W andlw b'00000001' ;maintain sanity addwf PCL, F ;quick test for 0 or 1 goto ClrWorkBit ;must be 0 (clr bit) SetWorkBit ;must be 1 (set bit) clrc rlf TEMP2, W ;get bit position * 2 (0, 2, 4 .. 14) addwf PCL, F ;bump PC, turn bit on then return bsf INDF, 0 return bsf INDF, 1 return bsf INDF, 2 return bsf INDF, 3 return bsf INDF, 4 return bsf INDF, 5 return bsf INDF, 6 return bsf INDF, 7 return ClrWorkBit clrc rlf TEMP2, W ;get bit position * 2 (0, 2, 4 .. 14) addwf PCL, F ;bump PC and turn it off then return bcf INDF, 0 return bcf INDF, 1 return bcf INDF, 2 return bcf INDF, 3 return bcf INDF, 4 return bcf INDF, 5 return bcf INDF, 6 return bcf INDF, 7 return ;------------------------------------------------------------- ;GetWorkBit -- ; at bit offset rombit_idx (1 relative) ; Entry: ; rombit_idx - contains one relative bit offset from rom work area (work0..work7) ; of bit to retrieve value of ; Exit: ; work0..work7(rombit_idx) -> W ;-------------------------------------------------------------- GetWorkBit call SetupFSR ;point to the bit in question clrc rlf TEMP2, W ;get bit position * 2 into w addwf TEMP2, W ;compute w = bit offset * 3 (0, 3, 6 ...) addwf PCL, F ;bump PC to jump to appropriate test ;Bit 0 btfss INDF, 0 ;Is bit set(1) retlw d'0' ; No, return 0 retlw d'1' ; Yes, return 1 ;Bit 1 btfss INDF, 1 ;Is bit set(1) retlw d'0' ; No, return 0 retlw d'1' ; Yes, return 1 ;Bit 2 btfss INDF, 2 ;Is bit set(1) retlw d'0' ; No, return 0 retlw d'1' ; Yes, return 1 ;Bit 3 btfss INDF, 3 ;Is bit set(1) retlw d'0' ; No, return 0 retlw d'1' ; Yes, return 1 ;Bit 4 btfss INDF, 4 ;Is bit set(1) retlw d'0' ; No, return 0 retlw d'1' ; Yes, return 1 ;Bit 5 btfss INDF, 5 ;Is bit set(1) retlw d'0' ; No, return 0 retlw d'1' ; Yes, return 1 ;Bit 6 btfss INDF, 6 ;Is bit set(1) retlw d'0' ; No, return 0 retlw d'1' ; Yes, return 1 ;Bit 7 btfss INDF, 7 ;Is bit set(1) retlw d'0' ; No, return 0 retlw d'1' ; Yes, return 1 ;---------------------------------------------------------------------- ; SetupFSR -- Point FSR at byte within work area determined by rombit_idx ; Entry: ; rombit_idx contians bit number (one relative) we need to point to ; Exit: ; FSR - pointing at byte within work0..work7 ; TEMP1 - zero relative byte offset (0,1,..7) ; TEMP2 - zero relative(0,1,..7) bit offset within byte ;----------------------------------------------------------------------- SetupFSR ;Setup FSR, TEMP1(byte offset), and TEMP2(bit offset) decf rombit_idx, W ;convert index to 0 relative movwf TEMP1 ; and temp byte offset area andlw b'00000111' ;strip off byte offset leaving bit offset only movwf TEMP2 ; and save into temp bit offset area clrc ;right justify the byte offset in TEMP1 rrf TEMP1, F ; by right shifting clrc ; and stripping 3 LSB's rrf TEMP1, F clrc rrf TEMP1, F ;Get FSR pointing at appropriate byte in work area (work0, work1 ...) movlw work0 ;Point FSR at beginning of work area movwf FSR movfw TEMP1 ;get byte offset (0 relative) addwf FSR, F ; point FSR straight at it return Hope this helps > > -- > http://www.piclist.com hint: The list server can filter out subtopics > (like ads or off topics) for you. See http://www.piclist.com/#topics > > -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.