fpga-lab-2/HDL/dec.sv

module dec
#(m = 32) 
(
	//clock and reset
	input logic clk, clrn,
	//control slave
	input logic ctl_wr, ctl_rd,
	input logic ctl_addr,
	input logic [31:0] ctl_wrdata,
	output logic [31:0] ctl_rddata,
	//memory slave
	input logic ram_wr,
	input logic [3:0] ram_addr,
	input logic [31:0] ram_wrdata,
	//external ports
	input logic train,
	output logic red, yellow, green
);
	
	logic run;
	logic [1:0] divider;
	
	logic [m-1:0] divisor;
	logic [1:0] contr;
	logic [2:0] colors;
	logic [m-1:0] cntdiv;
	logic enacnt;

	//control slave logic
	always_ff @ (posedge clk or negedge clrn)
	begin
		if (!clrn) 
		begin
			run <= 0;
			divider <= 0;
		end
		else
		begin
			if (ctl_wr)
			begin
				case (ctl_addr)
				1'b0: run <= ctl_wrdata[0];
				1'b1: divider <= ctl_wrdata[1:0];
				endcase
			end
		end
	end
	
	always_comb
	begin
		case (ctl_addr)
		1'b0: ctl_rddata = {31'b0,run};
		1'b1: ctl_rddata = {30'b0,divider};
		default: ctl_rddata = 'bx;
		endcase
	end
		
	//semaphore logic
	
	always_ff @ (posedge clk or negedge clrn)
	begin
		if (!clrn) cntdiv<=0;
		else
		begin
			if (train | ~run) cntdiv<=0;
			else
			begin
				if (enacnt) cntdiv<=0;
				else cntdiv<=cntdiv+1;
			end
		end
	end
	
	always_comb
	begin
		enacnt=(cntdiv==divisor);
	end
	
	always_ff @ (posedge clk or negedge clrn)
	begin
		if (!clrn) 
		begin
			colors <= 3'b100;
		end
		else
		begin
			if (train | ~run)
			begin
				colors <= 3'b100;
			end
			else
			begin
				if (enacnt)
				begin
					case (colors)
					3'b100: colors <= 3'b010;
					3'b010: colors <= 3'b011;
					3'b011: colors <= 3'b001;
					3'b001: colors <= 3'b001;
					default: colors <= 3'b100;
					endcase
				end
			end
		end
	end
	
    always_comb
    begin
        case (colors)
        3'b100: contr = 2'b00;
        3'b010: contr = 2'b01;
        3'b011: contr = 2'b10;
        3'b001: contr = 2'b11;
        default : contr = 2'b00;
        endcase
    end
    
	assign red = colors[2];
	assign yellow = colors[1];
	assign green = colors[0];

	periodram	b2v_inst3(
		.clock(clk),
		.data (ram_wrdata),
		.wraddress (ram_addr),
		.wren (ram_wr),
		.rdaddress({divider,contr}),
		.q(divisor)
	);

endmodule