INTEL_8259.v

module RS_PIC(p, reset_, intr, inta, index, irr7_irr0, reset_irr);
	input p, reset_, inta;
	input [7:0] irr7_irr0;
	output intr;
	output [7:0] reset_irr;
	output [2:0] index;
	
	reg [ :0] STAR;
	reg [2:0] INDEX;
	reg [7:0] RESET_IRR;
	reg INTR;
	
	assign intr = INTR;
	assign reset_irr = RESET_IRR;
	assign index = INDEX;
	
	parameter S0 = ...
	
	always @(posedge p or negedge reset_)
		if (reset_ == 0) begin
			STAR <= RS; INTR <= 0; RESET_IRR <= 'HFF;
		end else
			casex (STAR)
			RS: STAR <= S0; // wait per un reset sicuro
			S0: begin
				RESET_IRR <= 0; INTR <= (irr7_irr0 == 'H00) ? 0 : 1;
				INDEX <= priority_encoder(irr7_irr0);
				STAR <= (inta == 1) ? S1 : S0; end
			S1: begin
				INTR <= 0; STAR <= (inta == 1) ? S1 : S2; end
			S2: begin
				RESET_IRR <= decoder(INDEX); STAR <= S0;
			
			endcase
			
	function [2:0] priority_encoder;
		input [7:0] irr7_irr0;
		casex (irr7_irr0)
			'B???????1: priority_encoder = 'B000;
			'B??????10: priority_encoder = 'B001;
			'B?????100: priority_encoder = 'B010;
			'B????1000: priority_encoder = 'B011;
			'B???10000: priority_encoder = 'B100;
			'B??100000: priority_encoder = 'B101;
			'B?1000000: priority_encoder = 'B110;
			'B10000000: priority_encoder = 'B111;
			default:    priority_encoder = 'BXXX;
		endcase
	endfunction
	
	function [7:0] decoder;
		input [2:0] INDEX;
		casex (INDEX)
			'B000: decoder = 'B00000001;
			'B001: decoder = 'B00000010;
			'B010: decoder = 'B00000100;
			'B011: decoder = 'B00001000;
			'B100: decoder = 'B00010000;
			'B101: decoder = 'B00100000;
			'B110: decoder = 'B01000000;
			'B111: decoder = 'B10000000;
		endcase
	endfunction
	
endmodule