long addresa = 0;
byte towrite = 0;
byte rdval = 0;
byte mode = 0;
unsigned int velkost = 32768;

void setup() {

  digitalWrite(5, HIGH);
  digitalWrite(A0, HIGH);
  pinMode(2, OUTPUT);  // srclk
  pinMode(3, OUTPUT);  // serial data
  pinMode(4, OUTPUT);  // ltclk
  pinMode(5, OUTPUT);  // WEb (write enable (act low))
  pinMode(6, OUTPUT);    // D0
  pinMode(7, OUTPUT);    // D1
  pinMode(8, OUTPUT);    // D2
  pinMode(9, OUTPUT);    // D3
  pinMode(10, OUTPUT);   // D4
  pinMode(11, OUTPUT);   // D5
  pinMode(12, OUTPUT);   // D6
  pinMode(13, OUTPUT);   // D7
  pinMode(A0, OUTPUT); // OEb (output enable (act low))
  Serial.begin(115200);
  delay(500);
  Serial.println(" ");
  delay(500);
}

void shift(unsigned int adres) {
  digitalWrite(4, LOW);
  byte addres1 = adres >> 8;
  unsigned int addresint = adres << 8;
  byte addres2 = addresint >> 8;

  shiftOut(3, 2, MSBFIRST, addres1);
  shiftOut(3, 2, MSBFIRST, addres2);

  digitalWrite(4, HIGH);
}

void dataWR(byte datta) {
  // writes data to the 8 last free digital pins
  digitalWrite(A0, HIGH);

  pinMode(6, OUTPUT);    // D0
  pinMode(7, OUTPUT);    // D1
  pinMode(8, OUTPUT);    // D2
  pinMode(9, OUTPUT);    // D3
  pinMode(10, OUTPUT);   // D4
  pinMode(11, OUTPUT);   // D5
  pinMode(12, OUTPUT);   // D6
  pinMode(13, OUTPUT);   // D7

  byte bit0 = datta & 1;
  byte bit1 = datta & 2;
  byte bit2 = datta & 4;
  byte bit3 = datta & 8;
  byte bit4 = datta & 16;
  byte bit5 = datta & 32;
  byte bit6 = datta & 64;
  byte bit7 = datta & 128;

  digitalWrite(6, bit0);
  digitalWrite(7, bit1);
  digitalWrite(8, bit2);
  digitalWrite(9, bit3);
  digitalWrite(10, bit4);
  digitalWrite(11, bit5);
  digitalWrite(12, bit6);
  digitalWrite(13, bit7);
}

byte dataRD(unsigned int addr) {
byte daata = 0;

  digitalWrite(A0, LOW);

  pinMode(6, INPUT_PULLUP);
  pinMode(7, INPUT_PULLUP);
  pinMode(8, INPUT_PULLUP);
  pinMode(9, INPUT_PULLUP);
  pinMode(10, INPUT_PULLUP);
  pinMode(11, INPUT_PULLUP);
  pinMode(12, INPUT_PULLUP);
  pinMode(13, INPUT_PULLUP);

  daata = (128 * digitalRead(13)) + (64 * digitalRead(12)) + (32 * digitalRead(11)) + (16 * digitalRead(10)) + (8 * digitalRead(9)) + (4 * digitalRead(8)) + (2 * digitalRead(7)) + (1 * digitalRead(6));

return daata;
}

byte MEMread(unsigned int addrs) {
  // reads a byte at an address, also takes amount of bits (both values are mandatory)
  byte udaj = 0;
  shift(addrs);
  udaj = dataRD(addrs);

  return udaj;
}

void MEMwrite(unsigned int adrs, byte bajt) {
  digitalWrite(A0, HIGH);
  dataWR(bajt);
  shift(adrs);
  delayMicroseconds(10);
  digitalWrite(5, LOW);  // pulses WE low to write
  delayMicroseconds(500);  // assumes you use RC high pass filter with time constant <1000ns
  digitalWrite(5, HIGH);
}

void MEMdump(unsigned int maxaddr) {
  for (unsigned long y = 0; y < maxaddr; y = y + 16) {
  byte udaje[16];
    for (byte z = 0; z <= 15; z = z + 1) {
      unsigned long offset = z + y;
      udaje[z] = MEMread(offset);
      delayMicroseconds(5);
    }
    char buf[120];
    sprintf(buf, "%05x:  %02x %02x %02x %02x %02x %02x %02x %02x %02x %02x %02x %02x %02x %02x %02x %02x", 
    y, udaje[0], udaje[1], udaje[2], udaje[3], udaje[4], udaje[5], udaje[6], udaje[7], udaje[8], 
    udaje[9], udaje[10], udaje[11], udaje[12], udaje[13], udaje[14], udaje[15]);
    Serial.println(buf);
  }

}

void MEMerase() {
  for(long w = 0; w < velkost; w = w + 1) {
    MEMwrite(w, 255);
    delayMicroseconds(5);
  }
}

void MEMprogbulk() {
      addresa = 0;
      while (addresa < velkost) {

        if(Serial.available()) {

          towrite = Serial.parseInt();
          Serial.print("Writing ");
          Serial.print(towrite);
          Serial.print(" address: ");
          Serial.print(addresa);
          MEMwrite(addresa, towrite);
          Serial.print("   Wrote ");
          Serial.print(towrite);
          Serial.print(" address: ");
          Serial.println(addresa);

          addresa = addresa + 1;

          while(Serial.available()) {Serial.read();}
        }

      }

}

void loop() {

  if (Serial.available()) {

    mode = Serial.parseInt();

    if (mode == 0) {  // if mode is read
      addresa = Serial.parseInt();
      rdval = MEMread(addresa);
      Serial.print("Read data: ");
      Serial.print(rdval);
      Serial.print(" From address: ");
      Serial.println(addresa);
    }

    if (mode == 1) { // if mode is write
      addresa = Serial.parseInt();
      towrite = Serial.parseInt();
      MEMwrite(addresa, towrite);
      Serial.print("Written data: ");
      Serial.print(towrite);
      Serial.print(" To address: ");
      Serial.println(addresa);
    }

    if(mode == 2) {
      unsigned int maxadr = Serial.parseInt();
      Serial.println("Dumping Memory...");
      MEMdump(maxadr);
      Serial.println("Memory Dumped");
    }

    if(mode == 3) {
      Serial.println("Erasing Memory...");
      MEMerase();
      Serial.println("Memory Erased");
    }

    if(mode == 4) {
      MEMprogbulk();
    }

    while(Serial.available()) {
      Serial.read();
    }

  }

}




/*
  for(int i = 0; i <= 15; i = i + 1) {
  sbit = valtosr & (0b1000000000000000 >> i);

  if(sbit >= 1) {
  digitalWrite(3, HIGH);
  }

  if(sbit == 0) {
  digitalWrite(3, LOW);
  }
*/