DE0 Hex 4-digit counter (zero suppress) submodule: segleddec,unchat,cntb.

cntb.v

// ()MAXCNT-1)bit freerun counter
//
module cntb(clk,rst, q);

  parameter cntb_MAXCNT=15; // default 15:0
	input clk;
	input rst;
	output [cntb_MAXCNT:0] q;
	reg [cntb_MAXCNT:0] cnt;
 
	assign q=cnt;

	always @(posedge clk or posedge rst) begin
		if (rst==1'b1)
			cnt=0;
		else
			cnt=cnt+1;
	end
 endmodule

hexcounter.v

// terasIC DE0 topmodule skeleton
// onboard I/O 3-button,10-sw,10-LED,4-7SEG
//
// HEX 4digit-counter (zero suppress)
//
module hexcounter(clk,btn,sw,led,hled0,hled1,hled2,hled3,lcd_bl);
  input clk;
	input [2:0] btn;
	input [9:0] sw;
	output [9:0] led;
	output [7:0] hled0;
	output [7:0] hled1;
	output [7:0] hled2;
	output [7:0] hled3;
	output lcd_bl;

	wire rst;
	wire [47:0] cnt;
	wire [2:0] s_btn;
	wire [9:0] s_sw;
	wire bout3_2,bout2_1,bout1_0,bout0_0;
	wire clk_ms;
	wire [14:0] dmy;

	cntb #(15) freerun(clk,1'b0,{clk_ms,dmy[14:0]});
   cntb #(39) cnt40b_1(clk,rst, cnt);

	unchat unchat_btn2(clk_ms,btn[2], s_btn[2]);
	unchat unchat_sw0(clk_ms,sw[0],s_sw[0]);
	unchat unchat_sw1(clk_ms,sw[1],s_sw[1]);
	unchat unchat_sw2(clk_ms,sw[2],s_sw[2]);
	unchat unchat_sw3(clk_ms,sw[3],s_sw[3]);
	unchat unchat_sw4(clk_ms,sw[4],s_sw[4]);
	unchat unchat_sw5(clk_ms,sw[5],s_sw[5]);
	unchat unchat_sw6(clk_ms,sw[6],s_sw[6]);
	unchat unchat_sw7(clk_ms,sw[7],s_sw[7]);
	unchat unchat_sw8(clk_ms,sw[8],s_sw[8]);
	unchat unchat_sw9(clk_ms,sw[9],s_sw[9]);
	
	segleddec seg0(cnt[27:24],1'b0,1'b0, hled0,bout0_0);	// Digit xxx0 always on
	segleddec seg1(cnt[31:28],1'b0,bout2_1, hled1,bout1_0);
	segleddec seg2(cnt[35:32],1'b0,bout3_2, hled2,bout2_1);
	segleddec seg3(cnt[39:36],1'b0,1'b1, hled3,bout3_2);

	assign rst=~s_btn[2];
	
	// assign led[9:0]=cnt[31:(31-9)];
	assign led[9:0]=s_sw[9:0];
	
endmodule

segleddec.v

// 7segment LED decoder(anode common)
// support zero suppress
//
module segleddec(bcd,dp,bin, led,bout);
  input [3:0] bcd;
	input dp;	// decimal point
	input bin;
	output [7:0] led;
	output bout;

	assign bout=(bcd==4'b0000)?1'b1:1'b0;	// ~&bcd
	assign led=(bout&&bin)?8'b11111111:ALED(bcd,dp);
	
	function [7:0] ALED;
		input [3:0] bcd;
		input dp;
		case(bcd)
			4'h0:	ALED={ ~dp, 7'b1000000 }; // 0
			4'h1:	ALED={ ~dp, 7'b1111001 }; // 1
			4'h2:	ALED={ ~dp, 7'b0100100 }; // 2
			4'h3:	ALED={ ~dp, 7'b0110000 }; // 3
			4'h4:	ALED={ ~dp, 7'b0011001 }; // 4
			4'h5:	ALED={ ~dp, 7'b0010010 }; // 5
			4'h6:	ALED={ ~dp, 7'b0000011 }; // 6
			4'h7:	ALED={ ~dp, 7'b1111000 }; // 7
			4'h8:	ALED={ ~dp, 7'b0000000 }; // 8
			4'h9:	ALED={ ~dp, 7'b0011000 }; // 9
			4'ha:	ALED={ ~dp, 7'b0001000 }; // A
			4'hb:	ALED={ ~dp, 7'b0000011 }; // B
			4'hc:	ALED={ ~dp, 7'b0100111 }; // C
			4'hd:	ALED={ ~dp, 7'b0100001 }; // D
			4'he:	ALED={ ~dp, 7'b0000110 }; // E
			4'hf:	ALED={ ~dp, 7'b0001110 }; // F
			default:	ALED={ ~dp, 7'b1111111 }; // off
	endcase
	endfunction
endmodule

unchat.v

// un-chattering
//
module unchat(c_clk,inkey, s_key);

  input c_clk;	// 1-30ms
	input inkey;
	output s_key;
	
	reg hold;
	assign s_key=hold;
	
	always @(posedge c_clk) begin
		hold=inkey;
	end
endmodule