You would need to know what the core clock frequency of the processor is running at. If this is an ez-kit you are running off of, the external oscillator is 25 MHz. By looking at the values of the PLL_CTL and PLL_DIV registers in your application, you can figure out what the core clock and system clock of the processor are running at -- to do this, refer to the 561 hardware reference manual, around page 8-6:
Once you determine the core clock frequency, say its 500MHz, then you would need to loop 500 million times to reach a second. This will only work if your application is doing nothing else, and there are no interrupts enabled! Instead of this method, I would recommend that you use a core or general purpose timer to do your timing, where the core timers are incremented by the core clock, and gp timers by the system clock -- see page 15-1 of the hardware reference for more information on how to use them.
There is also an example in your VDSP install, located at:
<your install path>\Analog Devices\VisualDSP 5.0\Blackfin\Examples\ADSP-BF561 EZ-KIT Lite\Timer (C)
Tom is right -- it is better to use the timer. But if you want to implement a sit and spin loop, be sure that the compiler does not optimize the loop away. You can use the keyword "volatile" to ensure that the loop doesn't get optimized out.
volatile int i;
fo (i=0;i<count;i++) ;
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