#include <p18f4320.h>
#include <delays.h>
#include <timers.h>
#include <pwm.h>

#pragma config WDT = OFF, OSC = INTIO2, LVP = OFF, MCLRE = OFF

void main (void);
void Write6850Status(const char);
void Write6850Data(const char);
char Read6850Status(void);
char Read6850Data();
void OutChar(const char);
char InChar(void);
void OutString(const rom char*);
char ReadRAM(const char);
void WriteRAM(const char, const char);
void OutHex(const char);
void OutOct(const char);

#define RD PORTAbits.RA5	//not RD
#define WR PORTAbits.RA6	//nor WR
#define IOM PORTAbits.RA7	//IO/not M
#define MCUALE PORTCbits.RC0	//Address latch enable output
#define MCUS1 PORTCbits.RC1		//S1 output

//echo program:
//const rom char buf[] = {076, 03, 0323, 020, 076, 021, 0323, 020, 0333, 020, 017, 0322, 010, 00, 0333, 021, 0323, 021, 0303, 010,00};
//const int NumBytes = 21;

//12k basic bootloader:
const rom char buf[] = {076, 03, 0323, 020, 076, 021, 0323, 020, 
			041, 0302, 077, 061, 032, 00, 0333, 020, 
			017, 0320, 0333, 021, 0275, 0310, 055, 0167,
			0300, 0351, 013, 000}; 
const int NumBytes = 28;

const rom char hexchar[] = {'0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'A', 'B', 'C', 'D', 'E', 'F'}; 


//----------------------------------------------------------------------------

void main (void)
{
	char i, j;

// OSC settings
  	OSCCONbits.IRCF2 = 1; //Set osc to be 8 MHZ
  	OSCCONbits.IRCF1 = 1;	//OSCCON<2:0> = 111;
  	OSCCONbits.IRCF0 = 1;	//

	PORTC = 0x40;	//HOLD = 1, not RESET = 0
	TRISC = 0x00;	//all outputs
  	PORTA = 0xF0;	//A11:A8 = 0, RD, WR, IO/M = 1
	TRISA = 0x00;	//All outputs
	PORTB = 0;		//A15:A12 = 0
  	TRISB = 0xF0;	//A16:A12 outputs, rest inputs
	PORTD = 0;
	TRISD = 0xFF;	//All inputs

//turn off analog
	ADCON1 = 0x0F;	//all digital I/O

// set up PWM for 9600 Baud rate clock output
  	OpenTimer2(TIMER_INT_OFF & T2_PS_1_1);
  	OpenPWM1(12);
  	SetDCPWM1(26);

	Delay100TCYx(100);  //10000 cycles

	Write6850Status(003);	//master reset
	Write6850Status(021);	//X16 clock, 8 bits, 2 stop bit

	OutString("\n\rWelcome to the Mini-Altair!\n\r");

	i = 0;
	while (i < NumBytes)
	{
		OutString("\n\r");
		OutOct(i);	//address
		OutString(":  ");
		for (j = 0; j < 8; ++j)
		{
			WriteRAM(i, buf[i]);
			OutOct(ReadRAM(i++));
			if (i > NumBytes) break;
			OutChar(' ');
		}
	}
	OutString("\n\r");

	Delay100TCYx(100);  //10000 cycles

	TRISA = 0xFF;	//all inputs
	TRISB = 0xFF;	//all inputs
	PORTD = 0;
	TRISE = 0x17;	//enable PSP, port E all inputs
	
	PORTC = 0x82;	//MCUALE = 0, MCUS1 = 1, HOLD = 0, not RESET = 1;

	while(1);	//wait forever
}

void Write6850Status(const char stat)
{	
	MCUS1 = 0;	//write
	PORTD = 020;	//register 0, status
	TRISD = 0;	//enable data output
	MCUALE = 1;	//pulse ALE to latch low byte of address
	MCUALE = 0;
	IOM = 1;	//IO port 
	WR = 0;		//enable
	PORTD = stat;	//write data
	WR = 1;
	TRISD = 0xFF;	//disable output
}

void Write6850Data(const char data)
{
	MCUS1 = 0;	//write
	PORTD = 021;	//register 1, data
	TRISD = 0;	//enable data output
	MCUALE = 1;	//pulse ALE to latch low byte of address
	MCUALE = 0;
	IOM = 1;	//IO port 
	WR = 0;		//enable
	PORTD = data;	//write data
	WR = 1;
	TRISD = 0xFF;	//disable output
}

char Read6850Data()
{
	char a;
	MCUS1 = 1;	//read
	PORTD = 021;	//register 1, data
	TRISD = 0;	//enable data output
	MCUALE = 1;	//pulse ALE to latch low byte of address
	MCUALE = 0;
	TRISD = 0xFF;	//input
	IOM = 1;	//IO port 
	RD = 0;		//enable
	a = PORTD;	//read
	RD = 1;
	return a;
}

char Read6850Status()
{
	char a;
	MCUS1 = 1;	//read
	PORTD = 020;	//register 0, status
	TRISD = 0;	//enable data output
	MCUALE = 1;	//pulse ALE to latch low byte of address
	MCUALE = 0;
	TRISD = 0xFF;	//input
	IOM = 1;	//IO port 
	RD = 0;		//enable
	a = PORTD;	//read
	RD = 1;
	return a;
}

void OutChar(const char c)
{
	while ((Read6850Status() & 0x02) == 0);	//wait for tx buffer empty
	Write6850Data(c);	//output character
}

char InChar()
{
	while ((Read6850Status() & 0x01) == 0);	//wait for rx buffer full
	return Read6850Data();	//input character
}

void OutString(const rom char* s)
{
	while(*s) OutChar(*s++);
}

char ReadRAM(const char address)
{
	char a;
	PORTD = address;	
	TRISD = 0;	//enable data output
	MCUALE = 1;	//pulse ALE to latch low byte of address
	MCUALE = 0;
	TRISD = 0xFF;	//input
	IOM = 0;	//memory
	RD = 0;		//enable
	a = PORTD;	//read
	RD = 1;
	return a;
}

void WriteRAM(const char address, const char data)
{
	PORTD = address;	//register 1, data
	TRISD = 0;	//enable data output
	MCUALE = 1;	//pulse ALE to latch low byte of address
	MCUALE = 0;
	IOM = 0;	//memory
	WR = 0;		//enable
	PORTD = data;	//write data
	WR = 1;
	TRISD = 0xFF;	//disable output
}

void OutHex(const char c)
{
	OutChar(hexchar[c >> 4]);
	OutChar(hexchar[c & 0x0F]);
}

void OutOct(const char c)
{
	OutChar(hexchar[c >> 6]);
	OutChar(hexchar[0x7 & (c >> 3)]);
	OutChar(hexchar[0x7 & c]);
}