HELP! can #use delay=xxx take a #define value?

[Bangheadondesk]

In an effort to make my code configurable by a customer I want them only to have to change one define to enable the on board clock multiplier ( x 4) on a PIC18F452. This is done elsewhere in my code and works fine. The problem is that I want the '#use delay=xxx' preprocessor command to take a calculated value and not a constant. i.e.

This works fine...

#define _CRYSTAL_FRQ 16000000 //system clock frequency
#use delay(clock= _CRYSTAL_FRQ ) //Tells compiler the crystal speed

What I want to do is...

#define _CRYSTAL_FRQ 4000000 //system clock frequency
#define _PLL_ENABLED //hardware clock multiplier

#ifdef _PLL_ENABLED
#define _DELAY ( _CRYSTAL_FRQ * 4 )
#else
#define _DELAY _CRYSTAL_FRQ
#endif

#use delay(clock= _DELAY ) //Tells compiler the crystal speed

If I compile this I get "USE parameter value is out of range Expecting number: "

Can anybody help. Time is a factor now

[Ttelmah]

You can use a #define to set a clock frequency, but the 'result', must be a fixed number, not a 'sum'.
The problem is that the internal code for #use delay(clock=xxx), will only accept a number. The macro expansion, does not actual generate a 'number', but a sum, which then has to be solved. So:

#define CFREQ 4000000
#use delay(clock=CFREQ)

will work fine, but:

#define CFREQ 4000000*4
#use delay(clock=CFREQ)

won't...
Could you work the input 'backwards'?.
If you put in the processor frequency, with a statement like:

#define PROC_FREQ 16000000
#define PLL
#ifdef PLL
#define CRYSTAL PROC_FREQ/4
#else
#define CRYSTAL PROC_FREQ
#endif

#use delay(clock=PROC-FREQ)

will then work, and 'CRYSTAL' will be available elsewhere.
The other way would be to explicitly generate the values for the particular clock rates available, and test for each possible value...

Best Wishes

[Bangheadondesk]

Thanks Ttelmah, I see now why it wont work. Unfortunately I cant implement what you were pondering. The idea is to specify the external crystal frequency (which must match the actual physical crystal) and just toggle that PLL define. Oh well, dont suppose theres any way of altering that CCS code?

[Ttelmah]

It is a pity, and it really should not be that difficult to change.
However it is worth saying, that provided the range of possible frequencies is not too large, you could do it (bulkily), with something like: