#include <reg66x.h>

/////////////////////////
//// PIN DEFINITIONS ////
/////////////////////////

// Port 0 - in - in from CPLD
#define inDigits P0

// Port 1 - all out - out to CPLD
sbit outClock = P1^0;
sbit outReset = P1^1;

// Port 2 - all out - out to display
#define outDisplay P2

// Port 3 - in/out - buttons & speaker & CPLD control
sbit btnStartStop = P3^3;  // in
sbit outAcknowledge = P3^7;// out

/////////////////////////////
//// DECLARE SUBROUTINES ////
/////////////////////////////

void setupTimer();
void setupInputs();
void runningLoop();
void timerCallback();
void digitsCallback();
void controlCallback();
void resetCPLD();

///////////////////////////
//// DECLARE VARIABLES ////
///////////////////////////
 
int modeState = 0;
unsigned char hunths, tenths, seconds, tenSecs;

////////////////////////
//// PROGRAMME CODE ////
////////////////////////

void main() {
    setupTimer();
    setupInputs();
    resetCPLD();
   runningLoop();   
}

void runningLoop() {
    while(1){
        outDisplay = tenSecs + 64;
        outDisplay = seconds + 128;
        outDisplay = tenths + 192;
        outDisplay = hunths + 0;
    }
}

void resetCPLD(){
    outReset = 1;
    outReset = 0;

    return;
}

void setupTimer() {
    TMOD = 0x01;        // M0 = 1 (Timer mode 1 - 16 bit mode)
    TL0 = 0xFF;         // 400Hz = 2304 delay count, 65535-2304 = 63231
    TH0 = 0xF6;         // TH0 = 0xF6 :: TL0(0xFF) = 0xF6FF = 63231
    ET0 = 1;                // T0 Interrupt enabled.
    EA = 1;             // Interrupts enabled.
    TR0 = 1;                // Begin timer.
   
    P2 = 0x00000000;
   
    return;
}

void setupInputs() {
    EA = 1;             // Interrupts enabled.
    IT0 = 1;                // Set on falling edge.
    IT1 = 1;                // Set on falling edge.
    EX0 = 1;            // Enable external interrupt 0.
    EX1 = 1;                // Enable external interrupt 1.
   
    modeState = 0;
    outAcknowledge = 0;
   
    return;
}

//////// INTERRUPT CALLBACKS ////////

void timerCallback() interrupt 1 using 2 {
   TR0 = 0;
    TL0 = 0xFF;         // 400Hz = 2304 delay count, 65535-2304 = 63231
    TH0 = 0xF6;         // TH0 = 0xF6 :: TL0(0xFF) = 0xF6FF = 63231
    TF0 = 0;
    TR0 = 1;                // Begin timer.
    outClock =~ outClock;   // Invert the clock output pin.
}

void digitsCallback() interrupt 0 {
    if(modeState == 0){
        seconds = inDigits & 0x0f;
    }else if(modeState == 1){
        tenSecs = inDigits & 0x0f;
    }else if(modeState == 2){
        hunths = inDigits & 0x0f;
    }else if(modeState == 3){
        tenths = inDigits & 0x0f;
    }
   
    if(modeState < 3){
        modeState++;
    }else{
        modeState = 0;
    }
   
    outAcknowledge = 1;
    outAcknowledge = 0;
}

void controlCallback() interrupt 2 {
    TR0 =~ TR0; 
}