AVR Freaks

edit2: I found this code snippet:

TCCR1A = 0;          // disable all PWM on Timer1 whilst we set it up

ICR1 = 19999 ;   // frequency is every 20ms

// Configure timer 1 for Fast PWM mode using ICR1, with no prescaling

TCCR1A = (1<<WGM11)
    TCCR1B = (1 << WGM13) | (1<<WGM12) | (1 << CS10);

Why is the PWM disabled before setting the ICR1 ?

//mega8, 8MHz
int main()       
{                    

   DDRB=255;

   TCCR1A |= (1 << COM1A1) | ( 1 << COM1B1 ) ; //set both to non inverting mode
   TCCR1A |= (1 << WGM11);
   TCCR1B |= (1 << WGM13) | (1 << WGM12);
   TCCR1B |= (1 << CS12);
   
   ICR1 = 65535;

   OCR1A = 30000;
   OCR1B = 30000;

   for(;;)
   {

   }                  
} 

/*************************************************************************
*               Servo Driver Program using  ATMEGA 8 					 *
*	           Uses Fast PWM   Type 14 on Datasheet                      *
*  Drives 1 or 2 Servo Motors    PB1 drives Servo 1;  PB2 Drives Servo 2 *
*          Input Pins PC0 and PC1 Control the direction of Servo 1		 *
*		   Input Pins PC2 and PC3 Control the direction of Servo 2		 *
*        PB3 can be used to bink an LED at 1hz to check timer setup		 *
*    Based on 180 degree Servos; if < 180 tighten up CCW and CW limits 	 *
*																		 *
*                   								 *
*                  Last Revision  11/19/09								 *
*************************************************************************/

#include 
#define F_CPU 1000000UL  // 1 MHz
#include 

#define CCW_Limit1   2100  //  Servo 1 Counter clockwise limit
#define CW_Limit1   500	   //  Servo 1  Clockwise limit
#define Servo1_speed  4    //  Control the speed of Servo 1; lower number = faster

#define CCW_Limit2   2100  //  Servo 2 CCW limit
#define CW_Limit2   500    //  Servo 2  CW limit
#define Servo2_speed  2    //  Control the speed of Servo 2; higher number= slower



int main (void) {

// Select  Timer 1 for Fast PWM using ICR1 by setting bits WGM13 and WGM12
//  CS10 is selected for prescaler = 1  
//  Using Fast PWM number 14 on Datasheet   
TCCR1B  = (1<< WGM13) | (1<<WGM12) | (1<<CS10);

//Need 50hz output (20MS); 1,000,000hz/sec /50hz = 20000sec;  so ICR1 is 20000
ICR1=20000;

DDRB |= _BV(1);  // Make  PB1 an output port for Servo 1
DDRB |= _BV(2);  // Make  PB2 an output port for Servo 2

DDRC |= 0x00;  // Port C Data direction is automatically input but be sure
// Enable pullups for switch detection on PBC 0-3
PORTC = (1<<0) | (1<<1)| (1<<2) | (1<<3);    

//  Set bits 7,5 & 1 for non-inverting mode, TCCR1A Mode 14 for Timer 1
TCCR1A = (2 << 4) | (2<<6) | (1<<WGM11); //Enable PWM on PB1 in non-inverted compare mode 2. 
// note 2<<4,  2 is equal to binary 10 shifted 4 places, equal to binary 100000
//TCCR1A |= 2 << 6;  // Enable PWM on PB2, binary 10000000
//  By "|" "or"ing  TCCR1A, we have set the bits as 10100000
//Then include 1<<WGM11;  Sure, I could have just used TCCR1A = 0xA2; 


OCR1A = 1500; //OCR1A is the actual output pulse to the servo1 on PB1.
//  OCR1A is pumping out a 1.5 ms pluse every 50 hz. 
//  This pulse is necessary to hold it in position.  
//  Changing this value will alter the servo position.

OCR1B = 1500;  //  OCR1B is output to server2 on PB2. This is center


while (1) {
       //  Test to see if servo 1 is working by cycling through range.
      //for (OCR1A = CW_Limit1; OCR1A <= CCW_Limit1;OCR1A ++)
	  // { _delay_ms(2);}
      //for (OCR1A = CCW_Limit1; OCR1A >= CW_Limit1;OCR1A --)
	   //{ _delay_ms(2);}

			  
     //Test on PB3 to see if timing is correct on STK500 led -uncomment next 3 lines
	 // Led should blink every second -if not clock speed or prescaler problem.      
     //DDRB ^= 1 << 3;
	 //_delay_ms (500);
	 

//CONTROLS SERVO 1 with buttons on PBC0  and PBC1

	if (((PINC & (1<<0)) == 0) && (OCR1A > CW_Limit1))  {
	    //_delay_ms(0.1);// pause a second for debouncing
		 if (((PINC & (1<<0)) == 0)) { // double check to make sure key pressed
			OCR1A --;  //Reduce OCR1A and Turn Servo 1 clockwise
			}
			_delay_ms(Servo1_speed);
           }
    if (((PINC & (1<<1)) == 0) && (OCR1A  CW_Limit2))  {
	   // _delay_ms(0.1);// pause a second for debouncing
		 if (((PINC & (1<<2)) == 0)) { // double check to make sure key pressed
			OCR1B --;  //Reduce OCR1B and Turn Servo 1 clockwise
			}  _delay_ms(Servo2_speed);
           }

    if (((PINC & (1<<3)) == 0) && (OCR1B