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Text File  |  1986-12-16  |  475b  |  18 lines
  1. /* 
  2.  *    setfreq -- sets PC's tone generator to run 
  3.  *    continuously at the specified frequency 
  4.  */ 
  5. #include <conio.h> 
  6. #include "timer.h" 
  7.  
  8. void 
  9. setfreq(f) 
  10. unsigned f;    /* frequency in Hertz (approximate) */ 
  11. { 
  12.     unsigned divisor = TIMER_CLK / f; 
  13.  
  14.     outp(TIMER_CTRL, TIMER_PREP);       /* prepare timer */ 
  15.     outp(TIMER_COUNT, (divisor & 0xFF));   /* low byte of divisor */ 
  16.     outp(TIMER_COUNT, (divisor >> 8));       /* high byte of divisor */ 
  17. } 
  18.