PSHDL 4-tap Fir Filter

simpleFir.pshdl

// simple 4 tap fir
// coeff's are power of two
package de.tuhh.hbubert.noiseCancel;

module simpleFir {
	param uint Width = 8;

	@clock in bit clk;
	@reset in bit rst;

	in int<Width> x;
	out register int<Width> y;

	register(resetValue = {0,0,0,0}) int<Width> tap[4];	

	// write output

	// [1, 1, 1, 1]	
	y = tap[0]
		+ tap[1]
		+ tap[2]
		+ tap[3];

	// how to const array?
	//register(resetValue = {-1, 3.75, 3.75, -1}) int<Width> coeff[4];
	//y = coeff[0] * tap[0]
	//	+ coeff[1] * tap[1]
	//	+ coeff[2] * tap[2]
	//	+ coeff[3] * tap[3];

		// low pass
		// [-1, 3.75, 3.75, -1]
//	y =
//		-1 * tap[0]																	// -1
//		+ 2* tap[1] + tap[1] + tap[1]/2 + tap[1]/4 	// +3.75
//		+ 2* tap[2] + tap[2] + tap[2]/2 + tap[2]/4 	// +3.75
//		-1 * tap[3];																// -1

	// shift!
	for (I={1:3}) {
		tap[I] = tap[I-1];
	}

	// read input
	tap[0] = x;
}