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void delayMicrosecondsInterruptible(unsigned int us)
{
// for a one-microsecond delay, simply return. the overhead
// of the function call yields a delay of approximately 1 1/8 us.
if (--us == 0)
return;
// the following loop takes a quarter of a microsecond (4 cycles)
// per iteration, so execute it four times for each microsecond of
// delay requested.
us <<= 2;
// account for the time taken in the preceeding commands.
us -= 2;
// busy wait
__asm__ __volatile__ ("1: sbiw %0,1" "\n\t" // 2 cycles
"brne 1b" :
"=w" (us) :
"0" (us) // 2 cycles
);
}
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