commodore.gen.tr

       +----+--+----+ 
  RAS* |1 o       40| XTAL2
  CAS* |2         39| XTAL1
   AD7 |3    T    38| CPUCLK        R-Y  on TMS9928A/TMS9929A
   AD6 |4    M    37| GROMCLK
   AD5 |5    S    36| COMVID        Y    on TMS9928A/TMS9929A
   AD4 |6         35| EXTVDP        B-Y  on TMS9928A/TMS9929A
   AD3 |7    9    34| RESET*/SYNC 
   AD2 |8    9    33| Vcc 
   AD1 |9    1    32| RD0
   AD0 |10   8    31| RD1 
  R/W* |11   A    30| RD2
   Vss |12        29| RD3
  MODE |13        28| RD4 
  CSW* |14        27| RD5
  CSR* |15        26| RD6
  INT* |16        25| RD7
   CD7 |17        24| CD0
   CD6 |18        23| CD1 
   CD5 |19        22| CD2
   CD4 |20        21| CD3
       +------------+

#define MODE 2
#define CSW 3
#define CSR 8
#define RESET 9
  
  
#define PORT_MANIPULATION

int bytePins[8] =   { 14, 15 , 16, 17, 4, 5, 6, 7 }; 

void setDBReadMode() {
  #ifdef PORT_MANIPULATION
  DDRD = DDRD & B00001111; // Set Pin 4..7 as inputs. High nibble of databus.
  DDRC = DDRC & B11110000; // Set Analog pin 0..3 as inputs      
  #else
  for (int i=0;i<8;i++) {
    pinMode(bytePins[i], INPUT);
  }
  #endif
}

void setDBWriteMode() {
  #ifdef PORT_MANIPULATION  
  DDRD = DDRD | B11110000; // Set Pin 4..7 as outputs. High nibble of databus.
  DDRC = DDRC | B00001111; // Set Analog pin 0..3 as outputs
  #else
  for (int i=0;i<8;i++) {
    pinMode(bytePins[i], OUTPUT);
  }  
  #endif
}

void reset() {
  Serial.println("Resetting");
  digitalWrite(RESET, HIGH);
  delayMicroseconds(100);
  digitalWrite(RESET, LOW);
  delayMicroseconds(5);  
  digitalWrite(RESET, HIGH);
}

inline void setPort(unsigned char value) {
    #ifdef PORT_MANIPULATION
    PORTD = (PIND & 0x0F) | (value & 0xF0);
    PORTC = (PINC & 0xF0) | (value & 0x0F);
    #else
    unsigned char mask = 1;
    for (int i=0;i<8;i++) {
      digitalWrite(bytePins[i], value & mask);
      mask = mask<<1;
    }    
    #endif    
}

inline unsigned char readPort() {
    unsigned char memByte = 0;    
    #ifdef PORT_MANIPULATION
    memByte  = (PIND & 0xF0) | (PINC & 0x0F);
    #else
    unsigned char mask = 1;
    for (int i=0;i<8;i++) {
      if (digitalRead(bytePins[i])) {
        memByte = memByte | mask;
      } 
      mask = mask<<1;
    }        
    #endif  
    
    return memByte;
}

//Writes a byte to databus for register access
void writeByte( unsigned char value) {  
    setDBWriteMode();
    setPort(value); 
    digitalWrite(MODE, HIGH);        
    digitalWrite(CSW, LOW);            
    delayMicroseconds(10);
    digitalWrite(CSW, HIGH);
    setDBReadMode();
}

//Reads a byte from databus for register access
unsigned char  readByte( ) {
    unsigned char memByte = 0;
    digitalWrite(MODE, HIGH);            
    digitalWrite(CSR, LOW);        
    delayMicroseconds(10);
    memByte = readPort();
    digitalWrite(CSR, HIGH);
    return memByte;
}

//Writes a byte to databus for vram access
void writeByteToVRAM( unsigned char value) {  
    setDBWriteMode();
    setPort(value); 
    digitalWrite(MODE, LOW);        
    digitalWrite(CSW, LOW);            
    delayMicroseconds(10);
    digitalWrite(CSW, HIGH);
    setDBReadMode();
}

//Reads a byte from databus for vram access
unsigned char  readByteFromVRAM( ) {
    unsigned char memByte = 0;
    digitalWrite(MODE, LOW);            
    digitalWrite(CSR, LOW);        
    delayMicroseconds(8);
    memByte = readPort();
    digitalWrite(CSR, HIGH);
    return memByte;
}

void setRegister(unsigned char registerIndex, unsigned char value) {
  writeByte(value);
  writeByte(0x80 | registerIndex);  
}

void setWriteAddress( unsigned int address) {
  writeByte((address & 0xFFC0)>>6);
  writeByte(0x40 | (address & 0x3F));  
}

void setReadAddress( unsigned int address) {
  writeByte((address & 0xFFC0)>>6);
  writeByte((address & 0x3F));  
}

void setup() {
  setDBReadMode();
  Serial.begin(9600);
  pinMode(MODE, OUTPUT);
  pinMode(RESET, OUTPUT);
  pinMode(CSW, OUTPUT);
  pinMode(CSR, OUTPUT);  
  
  digitalWrite(RESET, HIGH);
  digitalWrite(MODE, HIGH);  
  digitalWrite(CSW, HIGH);    
  digitalWrite(CSR, HIGH);  

  reset();
  delay(2000);

  setRegister(0, 0);
  setRegister(1, 0xD0);
  setRegister(7, 0x56);  
  
  Serial.println("Clearing RAM");
  setWriteAddress(0);
  for (int i = 0;i<16384;i++) {
    writeByteToVRAM(0);
  }
  Serial.println("RAM Cleared, testing");  
  setWriteAddress(0);
  for (int i = 0;i<256;i++) {
    writeByteToVRAM(i);
  }
  setReadAddress(0);
  for (int i = 0;i<256;i++) {
    unsigned char value = readByteFromVRAM();
    Serial.println(value);
  }
}


void loop() { 
  

}