On Tue, 17 Feb 2015 11:55:39 +0100
Gál Zsolt <tralitove...@freemail.hu> wrote:
> Hello,
>
> The CCPR1 is defined in a header file as an 8 bit special function register
> and not 16 bit special function register. So the compiler does its job
> perfectly in this situation.
>
> //==============================================================================
>
> extern __at(0x0FBE) __sfr CCPR1;
> extern __at(0x0FBE) __sfr CCPR1L;
> extern __at(0x0FBF) __sfr CCPR1H;
>
> The question is, why isn't defined CCPR1 as __sfr16.
> I don't know why. Probably the endianness not the same in the hardware as
> the SDCC requires. I think, the developers will answer this question.
>
This is the problem: Not unequivocal the treatment order of the bytes. For
example: Refer to the
TIMER1 module in 16 bit operation.
(PIC18F1320 data sheet - DS39605F-page 106 - "12.6 Timer1 16-Bit Read/Write
Mode")
(PIC18F2550 data sheet - DS39632E-page 133 - "12.2 Timer1 16-Bit Read/Write
Mode")
The reading and writing different. To my knowledge this difficult to optimize.
Károly
> So you should divide the value moving into two steps temporally while there
> will be better solution.
>
> Zsolt
>
> 2015-02-16 22:20 GMT+01:00 Tomas Nordin <tom...@kth.se>:
>
> > I am writing code for the PIC 18f2550 target. Forgot to mension.
> >
> > On Mon, Feb 16, 2015 at 10:16:20PM +0100, Nordin Tomas wrote:
> > > Hi
> > >
> > > I have a function that look like this:
> > >
> > > void set_ccp1_rc2(unsigned int match_cnt)
> > > {
> > > T1CONbits.TMR1ON = 0; // Stop timer.
> > > TMR1 = 0; //Clear timer.
> > > CCPR1 = match_cnt;
> > > CCP1CON = 0b00001001; // From here pin will be set. Cleared on
> > match.
> > > T1CONbits.TMR1ON = 1; // Roll the timer.
> > > }
> > >
> > > It translates after compile to this:
> > >
> > > S_timing__set_ccp1_rc2 code
> > > _set_ccp1_rc2:
> > > ; .line 87; SRC/timing.c void set_ccp1_rc2(unsigned int
> > match_cnt)
> > > MOVFF FSR2L, POSTDEC1
> > > MOVFF FSR1L, FSR2L
> > > MOVFF r0x00, POSTDEC1
> > > MOVFF r0x01, POSTDEC1
> > > MOVLW 0x02
> > > MOVFF PLUSW2, r0x00
> > > MOVLW 0x03
> > > MOVFF PLUSW2, r0x01
> > > ; .line 89; SRC/timing.c T1CONbits.TMR1ON = 0; // Stop
> > timer.
> > > BCF _T1CONbits, 0
> > > ; .line 90; SRC/timing.c TMR1 = 0; //Clear timer.
> > > CLRF _TMR1
> > > ; .line 91; SRC/timing.c CCPR1 = match_cnt;
> > > MOVF r0x00, W
> > > MOVWF _CCPR1
> > > ; .line 92; SRC/timing.c CCP1CON = 0b00001001; // From here
> > pin will be set. Cleared on match.
> > > MOVLW 0x09
> > > MOVWF _CCP1CON
> > > ; .line 93; SRC/timing.c T1CONbits.TMR1ON = 1; // Roll the
> > timer.
> > > BSF _T1CONbits, 0
> > > MOVFF PREINC1, r0x01
> > > MOVFF PREINC1, r0x00
> > > MOVFF PREINC1, FSR2L
> > > RETURN
> > >
> > > There is a problem with the running code on the device. It occurs to me
> > > that only one byte is written to the _CCPR1 register (MOVWF _CCPR1).
> > > Also I am confused to see direct writes to 16-bit equates in the
> > > assembly code, is that possible?
> > >
> > > Should the above translation work as intended or is there something
> > > funky?
> > >
> > > /
> > >
> > > Tomas
> >
> >
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>
>
>
> --
> ~~~~~~~~~~~~~~~~
> http://galzsolt.zzl.org
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