// Handel-C decade counter and test - for the Celoxica RC100 board

void increment_decade(unsigned 4 *count, unsigned 1 Hold);
unsigned 8 sevenseg(unsigned 4 bcd);

set clock = external_divide "A11" 2 with { rate = 40 };	// 80 MHz / 2

void main (void)
{
	// Declarations
	unsigned 1 stop;
	unsigned 4 count[2];
	unsigned 1 hold;
	unsigned 24 cycles;
	unsigned 8 seg1, seg2;

	// Hardware interface

	// Seven segment display 1
	interface bus_out () display1 (unsigned 8 out = seg1)
		with { data = {"AA14", "AA20", "W18", "Y18", "V17", "W14", "AB14", "V13"} };	// Segments[8:1]
	interface bus_out () enable1 (unsigned 1 out = 1)				// Enable 1 - active-low
		with { data = {"AA22"} };

	// Seven segment display 2
	interface bus_out () display2 (unsigned 8 out = seg2)
		with { data = {"Y13", "AB20", "AA19", "W17", "AA18", "AA13", "AB13", "W13"} };	// Segments[8:1]
	interface bus_out () enable2 (unsigned 1 out = 1)				// Enable 2 - active-low
		with { data = {"V20"} };

	// Initialisation
	par {
		stop = 0;
		count[0] = 0;
		count[1] = 0;
	}

	par {

		// Cycle counter - use this to divide the clock
		while (!stop) par {
			cycles++;
			hold = (cycles != 0xffffff);
		}

		// Call the counter
		while (!stop)
			increment_decade(count, hold);

		// Seven segment displays (active high) - musn't call these in parallel!
		while (!stop) {
			seg1 = sevenseg(count[1]);
			seg2 = sevenseg(count[0]);
		}
	}
}

// This function describes a two digit BCD counter

void increment_decade(unsigned 4 *count, unsigned 1 Hold)
{
	if (Hold)
		count[0] = count[0];		/* You have to do something! */
	else if ( count[0] == 9 ) par {	/* "par" ensures one cycle */
		count[0] = 0;
		if ( count[1] == 9 )
			count[1] = 0;
		else
			count[1]++;
	} else
		count[0]++;
}

// This function describes a BCD to seven-segment encoder.
// The display inputs are active high. At 80 MHz, it doesn't matter
// that this takes two clocks to execute.

unsigned 8 sevenseg(unsigned 4 bcd)
{
	unsigned 8 seg;
	switch (bcd) {
		case 0:
			seg = 0b00111111;
			break;
		case 1:
			seg = 0b00000110;
			break;
		case 2:
			seg = 0b01011011;
			break;
		case 3:
			seg = 0b01001111;
			break;
		case 4:
			seg = 0b01100110;
			break;
		case 5:
			seg = 0b01101101;
			break;
		case 6:
			seg = 0b01111100;
			break;
		case 7:
			seg = 0b00000111;
			break;
		case 8:
			seg = 0b01111111;
			break;
		case 9:
			seg = 0b01100111;
			break;
		default:
			seg = 0b10001000;
			break;
	}

	return seg;
}