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Здравствуйте! Можете обьеснить почему в этом коде работают 1 и 3 2 и 4 регистры одновременно а не 1 и 2 2 и 4 как должно.

#include <TimerOne.h>
#include <string.h>
#define AXIS_X 1
#define AXIS_Y 2
#define AXIS_Z 3

//--- Pin connected to ST_CP of 74HC595
int latchPin = 10;
//--- Pin connected to SH_CP of 74HC595
int clockPin = 13;
//--- Pin connected to DS of 74HC595
int dataPin = 11;
//--- Used for faster latching
int latchPinPORTB = latchPin - 8;
//holds value for all the pins, [x][y][z]
byte cube[16][16];

//Counts through the layers
int current_layer = 0;

//--- This process is run by the timer and does the PWM control
void iProcess(){
  //last layer store
  int oldLayerBit = current_layer + 2;
    
  //increment layer count
  current_layer++;
  if(current_layer >= 16){
    current_layer = 0;
  }
  
  //--- Run through all the shift register values and send them (last one first)
  // latching in the process
  latchOff();
  for (int i = 0 ; i < 2 ; i++){
    spi_transfer(cube[current_layer][i]);
  }
  
  //Hide the old layer
  digitalWrite(oldLayerBit, LOW);
  //New data on the pins
  latchOn();
  //new layer high
  digitalWrite(current_layer + 2, HIGH);
}

//--- Direct port access latching
void latchOn(){
  bitSet(PORTB,latchPinPORTB);
}
void latchOff(){
  bitClear(PORTB,latchPinPORTB);
}

//--- Used to setup SPI based on current pin setup
//    this is called in the setup routine;
void setupSPI(){
  byte clr;
  SPCR |= ( (1<<SPE) | (1<<MSTR) ); // enable SPI as master
  SPCR &= ~( (1<<SPR1) | (1<<SPR0) ); // clear prescaler bits
  clr=SPSR; // clear SPI status reg
  clr=SPDR; // clear SPI data reg
  SPSR |= (1<<SPI2X); // set prescaler bits
  delay(10);
}

//--- The really fast SPI version of shiftOut
byte spi_transfer(byte data)
{
  SPDR = ~data;        // Start the transmission
  loop_until_bit_is_set(SPSR, SPIF);
  return SPDR;     
}

void setup() {
  Serial.begin(9600);

  //layer pins
  for(int i = 2; i < 10; i++)
  {
    pinMode(i, OUTPUT);
  }

  pinMode(latchPin, OUTPUT);
  pinMode(clockPin, OUTPUT);
  pinMode(dataPin, OUTPUT);

  digitalWrite(latchPin,LOW);
  digitalWrite(dataPin,LOW);
  digitalWrite(clockPin,LOW);

  //--- Setup to run SPI
  setupSPI();

  //--- Activate the PWM timer
  Timer1.initialize(100); // Timer for updating pwm pins
  Timer1.attachInterrupt(iProcess);
}


void loop(){
  int i,x,y,z;
  
  while (true)
  {
    
    effect_planboing(AXIS_Y, 400);
    
  }
}

// ==========================================================================================
//   Effect functions
// ==========================================================================================

// Draw a plane on one axis and send it back and forth once.
void effect_planboing (int plane, int speedd)
{
  int i;
  for (i=0;i<16;i++)
  {
    fill(0x00);
        setplane(plane, i);
    delay_ms(speedd);

  }
}


// ==========================================================================================
//   Draw functions
// =========================================================================================

void setplane_y (int y)
{
  int z;
  if (y>=0 && y<16)
  {
    for (z=0;z<16;z++)
      cube[z][y] = 0xff;
  } 
}

void setplane (char axis, unsigned char i)
{
    switch (axis)
    {
       case AXIS_Y:
            setplane_y(i);
            break;
    }
}


// Fill a value into all 64 byts of the cube buffer
// Mostly used for clearing. fill(0x00)
// or setting all on. fill(0xff)
void fill (unsigned char pattern)
{
  int z;
  int y;
  for (z=0;z<16;z++)
  {
    for (y=0;y<16;y++)
    {
      cube[z][y] = pattern;
    }
  }
}


// Delay loop.
// This is not calibrated to milliseconds,
// but we had allready made to many effects using this
// calibration when we figured it might be a good idea
// to calibrate it.
void delay_ms(uint16_t x)
{
  uint8_t y, z;
  for ( ; x > 0 ; x--){
    for ( y = 0 ; y < 90 ; y++){
      for ( z = 0 ; z < 20 ; z++){
        asm volatile ("nop");
      }
    }
  }
}