Problem with simple constant code

Hi

Well, this is driving me nuts. I'm using Keil uVision C51 compiler for a
Cygnal 80C51F302 device

This is the code:

""""""""
#define SYSCLK   10000000  // SYSCLK frequency in Hz
#define SYSCLK_MINUTE 600000000 // (600E6)

unsigned long TimerCount;
unsigned int SampleRate;

TimerCount = SYSCLK_MINUTE / SampleRate;
""""""""""

If SampleRate is 6 for example, the result of TimerCount is 1525

When I would suspect it should be 100000000 (10E6)

Where's my mistake?

Thanks

Klaus

Klaus Vestergaard Kragelund <klauskvik@hotmail.com> wrote:

> """"""""
> #define SYSCLK   10000000  // SYSCLK frequency in Hz
> #define SYSCLK_MINUTE 600000000 // (600E6)

#define SYSCLK 		10000000UL
#define SYSCLK_MINUTE   (60*SYSCLK)

would be easier to maintain.  The UL suffix might even suffice to make
your problem go away.

> unsigned long TimerCount;
> unsigned int SampleRate;

unsigned int is a 16-bit type on that platform.  That's your problem
(along with the fact that Keil doesn't strictly follow ANSI integer
promotion rules unless you request that explicitly)

> TimerCount = SYSCLK_MINUTE / SampleRate;
> """"""""""

If the suffix doesn't do it already, you may have to case SampleRate to
(unsigned long) here.


-- 
Hans-Bernhard Broeker (broeker@physik.rwth-aachen.de)
Even if all the snow were burnt, ashes would remain.

"Hans-Bernhard Broeker" <broeker@physik.rwth-aachen.de> wrote in message
news:c59dlp$7po$3@nets3.rz.RWTH-Aachen.DE...
> Klaus Vestergaard Kragelund <klauskvik@hotmail.com> wrote:
>
> > """"""""
> > #define SYSCLK   10000000  // SYSCLK frequency in Hz
> > #define SYSCLK_MINUTE 600000000 // (600E6)
>
> #define SYSCLK 10000000UL
> #define SYSCLK_MINUTE   (60*SYSCLK)
>
> would be easier to maintain.  The UL suffix might even suffice to make
> your problem go away.
>
> > unsigned long TimerCount;
> > unsigned int SampleRate;
>
> unsigned int is a 16-bit type on that platform.  That's your problem
> (along with the fact that Keil doesn't strictly follow ANSI integer
> promotion rules unless you request that explicitly)
>
> > TimerCount = SYSCLK_MINUTE / SampleRate;
> > """"""""""
>
> If the suffix doesn't do it already, you may have to case SampleRate to
> (unsigned long) here.
>

Thanks Hans

Well, it turned out that wasn't the problem. The Debug window was not
reset - so it was specified as a 16 bit value there - no problem when I
fixed the representation to a 32 bit value :-)

Cheers

Klaus