// Program to perform functions of Altair front panel with 8085
// Compiler Microchip C18

#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 Stop(void);
void Jump(const char, const char);
void Deposit(const char);
void Next(void);
void Run(void);

#define S0 PORTCbits.RC0	//S0 8085 status line
#define S1 PORTCbits.RC1	//S1 8085 status line
#define RAMRDDIS PORTAbits.RA5	//notRAMRDDIS disable RAM read
#define nRAMWROUT PORTAbits.RA6	//notRAMWROUT force RAM write
#define nCSOUT PORTAbits.RA7		//notCSOUT force chip select line for PIC parallel slave port
#define STEP PORTBbits.RB4	//STEP  step one 8085 machine cycle
#define nRUNSTOP PORTBbits.RB5	//notRUN/STOP  put 8085 into wait states
#define nRESET PORTCbits.RC7	//notRESET  8085 reset line

//echo program:
/*
const rom char buf[] = {076, 03, 0323, 020, 076, 021, 0323, 020, 0333, 020, 017, 0322, 010, 020, 0333, 021, 0323, 021, 0303, 010, 020};
const char NumBytes = 21;
const char PL = 000;	//PC low 
const char PH = 020;	//PC high  

//4k 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, 00   
					   }; 
const char NumBytes = 28;
const char PL = 000;	//PC low 
const char PH = 00;	//PC high
*/

//Turnkey monitor
const rom char buf[] = {0x3E, 0x03, 0xD3, 0x10, 0x3E, 0x11, 0xD3, 0x10, 
0x31, 0x00, 0x7C, 0xCD, 0x4A, 0x7D, 0x3E, 0x2E, 
0xCD, 0x9F, 0x7D, 0xCD, 0x95, 0x7D, 0xFE, 0x4D,
0xCA, 0x24, 0x7D, 0xFE, 0x4A, 0xC2, 0x08, 0x7D, 
0xCD, 0x54, 0x7D, 0xE9, 0xCD, 0x54, 0x7D, 0x3E, 
0x23, 0xCD, 0x4A, 0x7D, 0x54, 0x5D, 0xCD, 0x76,
0x7D, 0x1A, 0x67, 0xCD, 0x7C, 0x7D, 0xCD, 0x55, 
0x7D, 0xEB, 0xDA, 0x28, 0x7D, 0x77, 0xBE, 0xCA, 
0x28, 0x7D, 0x3E, 0x3F, 0xCD, 0x9F, 0x7D, 0xC3,
0x08, 0x7D, 0x3E, 0x0D, 0xCD, 0x9F, 0x7D, 0x3E, 
0x0A, 0xC3, 0x9F, 0x7D, 0x06, 0x06, 0x03, 0x21, 
0x00, 0x00, 0xCD, 0x95, 0x7D, 0x4F, 0xFE, 0x20,
0x37, 0xC8, 0xE6, 0xB8, 0xEE, 0x30, 0xC2, 0x42, 
0x7D, 0x79, 0xE6, 0x07, 0x29, 0x29, 0x29, 0x85, 
0x6F, 0x05, 0xC2, 0x5A, 0x7D, 0xC9, 0x06, 0x06,
0xAF, 0xC3, 0x83, 0x7D, 0x06, 0x03, 0xE6, 0x29, 
0x17, 0x29, 0x17, 0x29, 0x17, 0xE6, 0x07, 0xF6, 
0x30, 0xCD, 0x9F, 0x7D, 0x05, 0xC2, 0x7F, 0x7D,
0x3E, 0x20, 0xC3, 0x9F, 0x7D, 0xDB, 0x10, 0x0F, 
0xD2, 0x95, 0x7D, 0xDB, 0x11, 0xE6, 0x7F, 0xF5, 
0xDB, 0x10, 0x0F, 0x0F, 0xD2, 0xA0, 0x7D, 0xF1,
0xD3, 0x11, 0xC9}; 
const int NumBytes = 171;
const char PL = 0x00;	//PC low 
const char PH = 0x7D;	//PC high


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


void main (void)
{
	int i;

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

	PORTC = 0x00;	//notRESET = 0
	TRISC = 0x03;	//all outputs except S0, S1
  	PORTA = 0xE0;	//RAMRDDIS = 1, notRAMWROUT = 1, notCSOUT = 1
	TRISA = 0x0F;	//A11:A8 inputs, rest outputs
	PORTB = 0x20;	//notRUN/STOP = 1, STEP = 0
  	TRISB = 0xCF;	//notRUN/STOP outputs, rest inputs
	PORTD = 0;
	TRISD = 0xFF;	//All inputs
	TRISE = 0x17;	//enable PSP, port E 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 = 5 milliseconds

	nRESET = 1;	//release reset

	Stop();
	Jump(PL, PH);

	for (i = 0; i < NumBytes; ++i)
	{
		Deposit(buf[i]);
		Next();
	}

	Jump(PL, PH);
	PORTD = 0;	//sense switch setting
	Run();

	while(1);
}

// Stop 8085 - put into wait state cycles - at next instruction fetch cycle
void Stop(void)
{
	nRUNSTOP = 1;	//stop
	Delay10TCYx(1);	//delay for 5 micro seconds
	while (!(S0 && S1))	//if S0 and S1 not both high (instruction fetch)
	{
		STEP = 1;
		STEP = 0;	//pulse STEP to go to next cycle
		Delay10TCYx(1); //delay for 5 micro seconds
	}	
}

//Jump to memory location (PL,PH) by jamming a JMP instruction 
void Jump(const char PL, const char PH)
{
	PORTD = 0303;	//JMP instruction
	RAMRDDIS = 1;	//disable RAM
	nCSOUT	= 0;	//force PSP select so value will be read from PSP

	STEP = 1;
	STEP = 0;	//pulse STEP to go to next cycle
	Delay10TCYx(1); //delay for 5 micro seconds

	PORTD = PL;	//low byte of address

	STEP = 1;
	STEP = 0;	//pulse STEP to go to next cycle
	Delay10TCYx(1); //delay for 5 micro seconds

	PORTD = PH;	//high byte of address

	STEP = 1;
	STEP = 0;	//pulse STEP to go to next cycle
	Delay10TCYx(1); //delay for 5 micro seconds

	nCSOUT = 1;		//don't force PSP select
	RAMRDDIS = 0;	//re-enable RAM
}

//Write value Data to current memory location
void Deposit(const char Data)
{
	PORTD = Data;
	RAMRDDIS = 1;	//disable RAM RD
	nCSOUT = 0;	//force PSP select - reading value from PSP
	nRAMWROUT = 0;	//pulse nRAMWROUT - writing to RAM
	nRAMWROUT = 1;
	nCSOUT = 1;
	RAMRDDIS = 0;
}

//Advance address to next location by jamming a NOP instruction
void Next(void)
{
	PORTD = 0;	//NOP instruction
	RAMRDDIS = 1;	//disable RAM
	nCSOUT	= 0;	//force PSP select

	STEP = 1;
	STEP = 0;	//pulse STEP to go to next cycle
	Delay10TCYx(1); //delay for 5 micro seconds

	nCSOUT = 1;		//don't force PSP select
	RAMRDDIS = 0;	//re-enable RAM
}

//Take 8085 out of wait states and start running
void Run(void)
{
	nRUNSTOP = 0;	//run
}