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> From: justin crooks <jcrooks@wyoming.com>
> To: piclist@mivvma.mit.edu
> Subject: Re: Conversion of byte to percentage (math corrected)
> Date: Thursday, May 21, 1998 11:11 AM
>
>
>
> ----------
> > From: justin crooks <jcrooks@wyoming.com>
> > To: pic microcontroller discussion list <PICLIST@MITVMA.MIT.EDU>
> > Subject: Re: Conversion of byte to percentage
> > Date: Thursday, May 21, 1998 10:58 AM
> >
> > Or, if you just need a super-fast approximation for a PIC 16C7x or
> similar
> > (in assembly)
> >
> > Byte/2 - Byte/8 +Byte/64=100(Byte)/256
> >
> >     bcf     STATUS,C
> >     rrf     BYTE,w  ; Byte / 2
> >     movwf   PERCENT
> >
> >     movwf   TEMP
> >
> >     bcf     STATUS,C
> >     rrf     TEMP,F
        rrf     TEMP,W
> >     andlw   0x1F    ;Byte / 8
> >     subwf   PERCENT,W
        btfsc   BYTE,7
        addlw   2
        btfsc   BYTE,6
        addlw   1       ;Add Byte / 64
        movwf   PERCENT
> >
> > Example: Byte = 0x80 (128)
> > divide by 2: 0x40 (64)
> > swap into TEMP, rotate left, and erase high 3 bits. TEMP=0x10 (16)
> > Subtract this value from percent: 0x30 (48%)
Add 2.  This gives 50%.
255: 127 - 31 + 3 = 99%
> >
> > ----------
> > > From: Keith Howell <keithh@ARCAM.CO.UK>
> > > To: PICLIST@MITVMA.MIT.EDU
> > > Subject: Re: Conversion of byte to percentage
> > > Date: Thursday, May 21, 1998 8:53 AM
> > >
> > > adrian aslett wrote:
> > > >
> > > > I have a need to convert a byte value into a percentage.
> > >
> > > By coincidence, I have to do the exact same thing
> > > to show a quantity (0-255) on a display of 0-99 bars.
> > >
> > > unsigned char   cByte;
> > > unsigned int    nPercent;
> > >
> > >         nPercent = (((int)cByte)*100)/256;
> > >
> > > and the division by 256 is identical to >>8,
> > > or just take the high byte.
> > >         0--> 0,
> > >         255 -> 99.