第08课 · 计数器

// counter.v — 三种计数器 // 4位二进制计数器（带使能、加载、同步复位） module binary_counter ( input clk, rst, en, load, input [3:0] din, output reg [3:0] q ); always @(posedge clk) begin if (rst) q <= 4'b0; else if (en) begin if (load) q <= din; else q <= q + 1; end end endmodule // BCD 计数器 (0-9 循环) module bcd_counter ( input clk, rst, en, output reg [3:0] q ); always @(posedge clk) begin if (rst) q <= 4'b0; else if (en) begin if (q == 4'd9) q <= 4'b0; else q <= q + 1; end end endmodule // 4位 Johnson 计数器 module johnson_counter ( input clk, rst, en, output reg [3:0] q ); always @(posedge clk) begin if (rst) q <= 4'b0; else if (en) q <= {~q[0], q[3:1]}; end endmodule

// tb_counter.v module tb_counter; reg clk, rst, en, load; reg [3:0] din; wire [3:0] bin_q, bcd_q, john_q; binary_counter u_bin (.clk(clk), .rst(rst), .en(en), .load(load), .din(din), .q(bin_q)); bcd_counter u_bcd (.clk(clk), .rst(rst), .en(en), .q(bcd_q)); johnson_counter u_john (.clk(clk), .rst(rst), .en(en), .q(john_q)); integer pass = 0, fail = 0; always #5 clk = ~clk; initial begin clk = 0; rst = 1; en = 0; load = 0; din = 0; #12; rst = 0; en = 1; // 二进制计数: 0→1→2→3→4→5 #10; if (bin_q !== 1) begin $display("FAIL bin:1 got %0d", bin_q); fail=fail+1; end else pass=pass+1; #10; if (bin_q !== 2) begin $display("FAIL bin:2 got %0d", bin_q); fail=fail+1; end else pass=pass+1; #10; if (bin_q !== 3) begin $display("FAIL bin:3 got %0d", bin_q); fail=fail+1; end else pass=pass+1; // 加载测试 load = 1; din = 4'd14; #10; if (bin_q !== 14) begin $display("FAIL load:14 got %0d", bin_q); fail=fail+1; end else pass=pass+1; load = 0; #10; if (bin_q !== 15) begin $display("FAIL bin:15 got %0d", bin_q); fail=fail+1; end else pass=pass+1; #10; if (bin_q !== 0) begin $display("FAIL bin:wrap got %0d", bin_q); fail=fail+1; end else pass=pass+1; // BCD 计数: 7→8→9→0→1 rst = 1; #10; rst = 0; repeat(7) #10; if (bcd_q !== 7) begin $display("FAIL bcd:7"); fail=fail+1; end else pass=pass+1; #10; if (bcd_q !== 8) begin $display("FAIL bcd:8"); fail=fail+1; end else pass=pass+1; #10; if (bcd_q !== 9) begin $display("FAIL bcd:9"); fail=fail+1; end else pass=pass+1; #10; if (bcd_q !== 0) begin $display("FAIL bcd:wrap got %0d", bcd_q); fail=fail+1; end else pass=pass+1; // Johnson 计数: 0→1→3→7→F→E→C→8→0 rst = 1; #10; rst = 0; if (john_q !== 4'b0000) begin $display("FAIL john:0"); fail=fail+1; end else pass=pass+1; #10; if (john_q !== 4'b0001) begin $display("FAIL john:1 got %b", john_q); fail=fail+1; end else pass=pass+1; #10; if (john_q !== 4'b0011) begin $display("FAIL john:3 got %b", john_q); fail=fail+1; end else pass=pass+1; #10; if (john_q !== 4'b0111) begin $display("FAIL john:7"); fail=fail+1; end else pass=pass+1; #10; if (john_q !== 4'b1111) begin $display("FAIL john:F"); fail=fail+1; end else pass=pass+1; #10; if (john_q !== 4'b1110) begin $display("FAIL john:E"); fail=fail+1; end else pass=pass+1; $display("========================================"); $display("计数器测试: PASS=%0d FAIL=%0d", pass, fail); if (fail == 0) $display("✅ 二进制+BCD+Johnson 计数器验证通过！"); else $display("❌ 存在失败！"); $display("========================================"); $finish; end endmodule