1802 talks to mega A

 /**
  *  CDP1802b6 21/3/203:47 Issues woth serial.available slowing down reads of 1802 data. Trying new Norwegian code.
  *  3:57, works witrh dummy commands.
  *  . Start of array use for instructions
 Had big problems with first TPB cycle. Seemed to get old address outp[ut on address bus low when
 ..it should have been zero after reset. Round about the 4th clock after reset, adress goes to old value before reset.
 ..Settles down into next cycles with consistent addresses 1,2,3,4. But adr=0 remains a problem. The read line doesn't seem to be
 ..activated on first cycle so maybe just nop in zero position and move on?
 ..Next, connect up BUS pins to C port on mega. Initially just output nops, then when needed by instruction fetch, then chnage
 .. to little program that plays with Q and does loop involving nops too. This program has too many diagnostic entries so will tidy up
 .. before trying next version.
 Tidied up and working with resistors connecting data bus to $C4 pattern = nop.
 Now going to send constant $C4 via PORTC of Mega2650 to breadboard containing 1802. PORTC-->BUS 1802 all the time. Should be the
 ..same as resistor to rail $C4 above. Worked 10:07
 Now try sending $c4 only when clk goes low and TPB is high.Worked 10:19.
 Now try sending nop from mega to 1802 bus only when 1) clock goes low,2) TPB is high and 3) read is low. Worked 10:24
 Now going to select nop from an array of nops. Worked with just one element of arry of instructions called vRAM[]. Do several next.
 Key change was [ byte vRAM[5] = {0xc4, 0xc4, 0xc4, 0xc4, 0x00}; ] Next add instructions to turn on and off Q flag.
 Now going to put in little sequence of instructions. Key change is: [ byte vRAM[5] = {0xc4, 0x7b, 0xc4, 0x7a, 0x00};
   //ie nop,seq,nop,req,idl ] Worked and got Q flag going on and off with this; [byte vRAM[5] = {0x7b, 0x7b, 0x7a, 0x7b, 0x00};  ]
   Now gpoing to turn Q on and off but with  branch back to start. Worked OK.
11:27am 20/3/20. Adding in dump of vertual ram array as well as issuing commands from serial terminal.
..Practiced some of the routines in dumper3.
Going well, apart from serial read issues, but basic 1820 stuff going well. Try new serial read instruction code.
*/

//1802 talks to Arduino Mega
#define clockPin 13
#define clearPin 12
#define TPBpin A1
#define readPin A15     //the *MRD of 1802
#define SC0pin A12      //When SC0=LOW it's a fetc h, when HI it's executing
#define DELAY 50

int val = 0; int bufBytes, TPBCtr, clkCtr = 0;
int adrByte=0;
//byte vRAM[5] = {0xc4, 0x7b, 0xc4, 0x7a, 0x00};             //ie nop,seq,nop,req,idl
//byte vRAM[5] = {0x7b, 0x7b, 0x7a, 0x7b, 0x00};             //ie nop,seq,nop,req,idl
byte vRAM[256] = {0x7b, 0x7a, 0x7b, 0x7a, 0x30, 0x00,0x00};             //ie seq,seq,req,seq,br start, idl
void setup() {

  pinMode(clockPin, OUTPUT);
  pinMode(clearPin, OUTPUT);
  pinMode(TPBpin,INPUT);
  pinMode(readPin,INPUT);
  pinMode(SC0pin,INPUT);
  DDRA=0x00;              //DDRA reads Adress port of 1802. All inputs
  DDRC=0x00;              //PORTC connects to 1802 data BUS.
  Serial.begin(9600);      // open the serial port at 9600 bps:
  serialFlush();
  Serial.flush();
  Serial.println("Arduino talks to 1802. Pb 2020");
  delay(500);
  doReset();
//  vRAM[1] = 0xc4;
  dumpVert();
}


void loop() {
 // SRB();
  norwayCommand();
  digitalWrite(clockPin, HIGH);   // turn the LED on (HIGH is the voltage level)
  delay(DELAY); // wait for a second
  digitalWrite(clockPin, LOW);    // turn the LED off by making the voltage LOW
  DDRC=0x00;          //DDRC usually input except when sending instruction
  clkCtr++;           //how many clocks after reset?

  if (digitalRead(TPBpin) ==HIGH) {
    doTPBWork();
  }
  delay(DELAY);                       // wait for a second
}
void doTPBWork(void) {
  TPBCtr++;
  //DDRC=0xff;            //make mega data port output
  //PORTC = 0xc4;          //send nop
  Serial.print("TPB with clock low. Num=");
  Serial.print(TPBCtr);
  Serial.print(" Clocks=");
  Serial.print(clkCtr);
  Serial.print(" AdrL=");
  adrByte = PINA;
  Serial.print(PINA,HEX);
  if (digitalRead(readPin)==LOW) {
    DDRC = 0xff;            //just for this version. Send nop when clk goes 1 to 0, TPB =1, MRD=0
    PORTC = vRAM[adrByte] ;   //0xc4;           //constant noop

    Serial.print(" %R ");
     Serial.print(vRAM[adrByte],HEX);
  }
  if(digitalRead(SC0pin)==LOW) {
    Serial.print(" F ");        //fetching instruction
  }
  else  {
    Serial.print(" E ");         //executing instruction
  }
  Serial.println(" ]");
}
void doReset(void){
  digitalWrite(clearPin,LOW);   //bring CLEAR low for about 10 clocks to reset 1802
  for(int i =0;i<=10;i++) {
      digitalWrite(clockPin, HIGH);
      delay(DELAY); // wait
      digitalWrite(clockPin, LOW);
      delay(DELAY);
  }// 10 clocks low should reset 1802
  digitalWrite(clearPin,HIGH);    //bring back to RUN mode

}
void serialFlush(){
  while(Serial.available() > 0) {   //while there are characters in the serial buffer, because Serial.available is >0
    char t = Serial.read();         // get one character
  }
}
void showLenOfTxBuffer(void) {
  bufBytes=Serial.availableForWrite();
  Serial.print(bufBytes);
  Serial.println("~");
}

void dumpVert(void) {
  char data[100];
  Serial.print("Col: ");
  for(int i=0;i<16;i++) {
    sprintf(data, "%02x  ",i);
    Serial.print(data);
    if(i==7) Serial.print(" ");
  }
  for (int i=0;i<256;i++){
    if (i%16 == 0){
      Serial.println ("");
      sprintf(data, "%02x ",i);
      Serial.print(data);
    }
    if(i%8==0) { Serial.print("|"); }
    sprintf(data, " %02x ",vRAM[i]);
    Serial.print(data);
  }
  Serial.println(" ");
}
void doDump(void) {
  Serial.println("Got a dump");
  dumpVert();
}
void doGetProgram(void){
  Serial.println("Doing getProgram.");
}
void SRB(){
  byte k;
  byte buff[10];
  k = Serial.readBytes(buff, 3);
  if (k>0) {
    //Serial.println(k);

    for (int i = 0;i<k;i++) {
     // Serial.println(buff[i],HEX);
    }
    if ((buff[0] ==0x64) && (buff[1] == 0x75 )) doDump();  //"du" = dump array
    if ((buff[0] ==0x67) && (buff[1] == 0x70 )) doGetProgram(); //"gp = get program, via serial
    //Serial.println("Got a dump");
  }
}
void norwayCommand(void){ //trying better instruction method from serial https://www.norwegiancreations.com/2017/12/arduino-tutorial-serial-inputs/
  String command;
   if(Serial.available()){
        command = Serial.readStringUntil('\n');

        if(command.equals("init")){
            Serial.print("i"); //nitialize();
        }
        else if(command.equals("send")){
             Serial.print("s");
        }
        else if(command.equals("data")){
             Serial.print("d");
        }
        else if(command.equals("reboot")){
             Serial.print("r");
        }
         else if(command.equals("du")){
             Serial.print("Dumper");
             dumpVert();
         }
        else{
            Serial.println("Invalid command");
        }
    }
}