I bought a breadboard from Maplin and some jump wires and put the ICs (intergrated circuits, that'll be the computer chips then), and some LEDs to the address pins of the Z80 and a bright blue LED on the clock. I did try initially putting the blue LED in-line but for some reason it wouldn't light up so I assumed it didnt have enough power to drive it (it was a HIGH line state before going into the inverter) , so I took a feed off the 'active low' state of the CLK signal from the 74LS04 and fed it back in and inverted the signal again and then connected the blue LED to that and it lit up like a dream. The hex inverters also have their own power supply and can boost a signal coming in. I think they're also known as 'buffers'.
Anyway, here it is all wired up ready to go:
This is the Arduino program I wrote to talk to the Z80:
/*
Zilog Z80 Controller
*/
const int CPU = 0;
const int PIN = 1;
const int DIR = 2;
const int STS = 3;
/* low states = true */
int CLK[4] = {06,13,OUTPUT,LOW}; // in
int INT[4] = {16,0,OUTPUT,LOW}; // in
int NMI[4] = {17,0,OUTPUT,LOW}; // in
int HALT[4] = {18,12,INPUT,LOW}; // out
int MREQ[4] = {19,11,INPUT,LOW}; // out
int IORQ[4] = {20,10,INPUT,LOW}; // out
int RD[4] = {21,9,INPUT,LOW}; // out
int WR[4] = {22,8,INPUT,LOW}; // out
int BUSACK[4] = {23,7,INPUT,LOW}; // out
int WAIT[4] = {24,0,OUTPUT,LOW}; // in
int BUSRQ[4] = {25,0,OUTPUT,LOW}; // in
int RESET[4] = {26,6,OUTPUT,LOW}; // in
int M1[4] = {27,5,INPUT,LOW}; // out
int RFSH[4] = {28,4,INPUT,LOW}; // out
int OLDM1[4] = {27,5,INPUT,LOW};
int T = 0;
void setup() {
// Define Pins
pinMode(CLK[PIN], CLK[DIR]);
pinMode(M1[PIN], M1[DIR]);
pinMode(RESET[PIN], RESET[DIR]);
pinMode(HALT[PIN], HALT[DIR]);
pinMode(MREQ[PIN], MREQ[DIR]);
pinMode(IORQ[PIN], IORQ[DIR]);
pinMode(RD[PIN], RD[DIR]);
pinMode(WR[PIN], WR[DIR]);
pinMode(BUSACK[PIN], BUSACK[DIR]);
pinMode(RFSH[PIN], RFSH[DIR]);
// Setup Serial Port
Serial.begin(9600);
// Reset CPU
Serial.println("CPU Reset");
delay(500);
RESET[STS]=HIGH;
digitalWrite(RESET[PIN],RESET[STS]);
delay(2000);
RESET[STS]=LOW;
digitalWrite(RESET[PIN],RESET[STS]);
}
void loop() {
//Start Clock Period T
digitalWrite(CLK[PIN],CLK[STS]);
delay(500);
// Read Machine Cycle Status M Clock High
M1[STS]=digitalRead(M1[PIN]);
HALT[STS]=digitalRead(HALT[PIN]);
MREQ[STS]=digitalRead(MREQ[PIN]);
IORQ[STS]=digitalRead(IORQ[PIN]);
RD[STS]=digitalRead(RD[PIN]);
WR[STS]=digitalRead(WR[PIN]);
BUSACK[STS]=digitalRead(BUSACK[PIN]);
RFSH[STS]=digitalRead(RFSH[PIN]);
Serial.print(T);
Serial.print("=");
Serial.print(CLK[STS]);
Serial.print(" M1=");
Serial.print(M1[STS]);
Serial.print(" HALT=");
Serial.print(HALT[STS]);
Serial.print(" MREQ=");
Serial.print(MREQ[STS]);
Serial.print(" IORQ=");
Serial.print(IORQ[STS]);
Serial.print(" RD=");
Serial.print(RD[STS]);
Serial.print(" WR=");
Serial.print(WR[STS]);
Serial.print(" RFSH=");
Serial.print(RFSH[STS]);
Serial.print(" BUSACK=");
Serial.print(BUSACK[STS]);
Serial.println();
if(M1[STS]==HIGH && OLDM1[STS]==LOW) {
Serial.println("----M1 Starts----");
}
OLDM1[STS]=M1[STS];
CLK[STS]=!CLK[STS];
T=T+CLK[STS];
}
