Прошу помочь понять принцип. не понимаю для чего тут CLK. как понимается что минус а что плюс.

const int interruptA = 0; / / Interrupt 0 (pin 2)

   const int interruptB = 1; / / Interrupt 1 (pin 3)

   int CLK = 2; / / PIN2

   int DAT = 3; / / PIN3

   int BUTTON = 4; / / PIN4

   int LED1 = 5; / / PIN5

   int LED2 = 6; / / PIN6

   int COUNT = 0;

   void setup ()

   {

   attachInterrupt (interruptA, RoteStateChanged, FALLING);

   / / AttachInterrupt (interruptB, buttonState, FALLING);

   pinMode (CLK, INPUT);

   digitalWrite (2, HIGH); / / Pull High Restance

   pinMode (DAT, INPUT);

   digitalWrite (3, HIGH); / / Pull High Restance

   pinMode (BUTTON, INPUT);

   digitalWrite (4, HIGH); / / Pull High Restance

   pinMode (LED1, OUTPUT);

   pinMode (LED2, OUTPUT);

   Serial.begin (9600);

   }

   void loop ()

   {

   if (! (digitalRead (BUTTON)))

   {

   COUNT = 0;

   Serial.println ("STOP COUNT = 0");

   digitalWrite (LED1, LOW);

   digitalWrite (LED2, LOW);

   delay (2000);

   }

   Serial.println (COUNT);

   }

   / / -------------------------------------------

   void RoteStateChanged () / / When CLK FALLING READ DAT

   {

   if (digitalRead (DAT)) / / When DAT = HIGH IS FORWARD

   {

   COUNT;

   digitalWrite (LED1, HIGH);

   digitalWrite (LED2, LOW);

   delay (20);

   }

   else / / When DAT = LOW IS BackRote

   {

   COUNT -;

   digitalWrite (LED2, HIGH);

   digitalWrite (LED1, LOW);

   delay (20);

   }

   }