I am trying output a clock and change its frequency dynamically with a rotary encoder.

When the code for the rotary encoder is included the clock doesn't reach its max freq(31Khz). But without the rotary encoder code, it does. What is happening that it can't reach its max freq?

const byte CLOCKOUT = 9;
int val;
int encoder0PinA = 3;
int encoder0PinB = 4;
int encoder0Pos = 0;
int encoder0PinALast = LOW;
int n = LOW;

void setup() {
  pinMode (CLOCKOUT, OUTPUT); 
  // set up Timer 1
  TCCR1A = bit (COM1A0);  // toggle OC1A on Compare Match
  TCCR1B = bit (WGM12) | bit (CS12);   // CTC, no prescaling
  OCR1A =  0;

  pinMode (encoder0PinA, INPUT);
  pinMode (encoder0PinB, INPUT);
  Serial.begin (9600);
}

void loop() {
  n = digitalRead(encoder0PinA);
  if ((encoder0PinALast == LOW) && (n == HIGH)) {
    if (digitalRead(encoder0PinB) == LOW) {
      OCR1A-=100;
    } else {
      OCR1A+=100;
    }
    Serial.print (OCR1A);
    Serial.print ("/");
  }
  encoder0PinALast = n;
}

I am trying output a clock and change its frequency dynamically with a rotary encoder.

When the code for the rotary encoder is included the clock doesn't reach its max freq(31Khz). But without the rotary encoder code, it does. What is happening that it can't reach its max freq?

const byte CLOCKOUT = 9;
int val;
int encoder0PinA = 3;
int encoder0PinB = 4;
int encoder0Pos = 0;
int encoder0PinALast = LOW;
int n = LOW;

void setup() {
  pinMode (CLOCKOUT, OUTPUT); 
  // set up Timer 1
  TCCR1A = bit (COM1A0);  // toggle OC1A on Compare Match
  TCCR1B = bit (WGM12) | bit (CS12);   // CTC, no prescaling
  OCR1A =  0;

  pinMode (encoder0PinA, INPUT);
  pinMode (encoder0PinB, INPUT);
  Serial.begin (9600);
}

void loop() {
  n = digitalRead(encoder0PinA);
  if ((encoder0PinALast == LOW) && (n == HIGH)) {
    if (digitalRead(encoder0PinB) == LOW) {
      OCR1A-=100;
    } else {
      OCR1A+=100;
    }
    Serial.print (OCR1A);
    Serial.print ("/");
  }
  encoder0PinALast = n;
}

The Code that reaches the Max freq properly is below

void setup ()
  {
  pinMode (CLOCKOUT, OUTPUT); 
  // set up Timer 1
  TCCR1A = bit (COM1A0);  // toggle OC1A on Compare Match
  TCCR1B = bit (WGM12) | bit (CS12);   // CTC, no prescaling
  OCR1A =  0;
  }

void loop (){
  }