di2608.txt 
;**************************************************************************************************
; LISTING 1 - FAN-DRIVER C FILE
;
; "Audio amp makes efficient fan controller," EDN, Nov 9, 2000, pg 182

; http://www.ednmag.com/ednmag/reg/2000/11092000/designideas.htm#23di8
;
***************************************************************************************************

#include "8saa.h"		     		 // Include file for the COP8SLB
void init_params();                  // Initializtion routine
void shutdown(unsigned int state);   // Shutdown amplifier routine
void fan_speed(unsigned int state);  // The Speed of the fan
                                     // Alters the PWM duty cycle
                                     // In percent of (on) vs (off)
void main(){

        init_params(); // initialize the parameters

        // Make sure the amplifier is on
        shutdown(0);

        // Scale up the fan speed

        // Turn up the fan speed
        fan_speed(20);

        // Scale down the fan

        //fan_speed(10);


        // Shutdown the amplifier (off)
        shutdown(1);

        while(1);  // forever loop

}

// The shutdown routine

void shutdown(unsigned int state){

if (state==0)

   PORTDD.0=0;     // Turn the pin low
   else
      PORTDD.0=1;  // else turn the pin high
 
}

// The intialization parameters

void init_params(){

        // Turn PWM on out

        PORTGC.3=1;   // Set so the portgc pin is high 
        PORTGD.3=1;   // Lower the portgd pin for PWM mode
       
        // Make the high byte zero

        T1RAHI=0;
        T1RBHI=0;

        // Set to PWM: TxA Toggle
        // Autoreload RA, RB

        CNTRL.T1C1=1;
        CNTRL.T1C2=0;
        CNTRL.T1C3=1;

}


// The change fan speed routine

void fan_speed (unsigned int state){


        // Detect if it is less or equal to 100 percent
        if (state<101){

           T1RALO=state;       // Initialize the state
           T1RBLO=state-100;   // Turn the lower half state-100
           CNTRL.T1C0=1;       // Set the timer enabled bit

          }

}