[stella] TIA audio mode 3 polynomial

[Adam Wozniak <adam@xxxxxxxxxxxxxxxx>]

#include <stdio.h>

// Ok, here's how the poly for mode 3 is generated
//
// Each incoming audio clock tick,
//   clock the 5 bit polynomial [5 3]
// Each time the 5 bit polynomial changes from 0 to 1 or 1 to 0,
//   clock the 4 bit polynomial [4 3]
// Output is the output of the 4 bit polynomial

int poly4(void)
{
	static int spot = 0;
	static int count = 0;
	static const int array[] = { 1, 2, 2, 1, 1, 1, 4, 3, -1 };

	count++;
	if (count == array[spot])
	{
		spot++;
		count = 0;
	}
	if (array[spot] == -1)
		spot = 0;
	return !(spot&1);
}

int poly5(void)
{
	static int spot = 0;
	static int count = 0;
	static const int array[] = { 5, 3, 2, 1, 3, 1, 1, 1, 1, 4, 1, 2, 1, 1, 2, 2, -1 };

	count++;
	if (count == array[spot])
	{
		spot++;
		count = 0;
	}
	if (array[spot] == -1)
		spot = 0;
	return !(spot&1);
}

void main (void)
{
	int out = 1;
	int now, then = -1;
	
	while(1)
	{
		now = poly5();
		if (now != then)
		{
			out = poly4();
		}
		then = now;
		printf("%d\n", out);
	}
}

-- 
adam@xxxxxxxxxxxxxxxx        http://cuddlepuddle.org/~adam/pgp.html
Will code for food.          http://cuddlepuddle.org/~adam/resume.html
"The dinosaurs are not around today because they did not have a space program."
  -- Arthur C. Clarke

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