将这段代码改为八进制计数器 module counter4 ( load , clr , c , DOUT , clk , up_down , DIN); input input input input input [3:0] output reg load ; clk; clr ; up_down ; DIN ; c ; c ; output [3:0] DOUT ; // 异步预置数 // 输入时钟 // 异步清零 // 加减计数 // 预置数输入 // 进位、借位 ，用于级联 // 计数输出 reg [3:0] data_r; assign DOUT = data_r; always @ ( posedge clk , posedge clr , posedge load) begin if ( clr = = 1) data_r < = 0; else if ( load = = 1) data_r < = DIN; else begin if ( up_down ==1) begin // 异步清零 // 异步预置数 //加计数 if ( data_r = = 4'b1001) begin data_r<= 4'b0000; c = 1; end else begin data_r<= data_r +1; c = 0 ; end else begin end //减计数 if ( data_r = = 4'b0000) begin data_r < = 4'b1001; c = 1; end else begin data_r < = data_r -1; c = 0 ; end end end end endmodule

module counter4 (input load, clr, c, clk, up_down, DIN, output reg [3:0] DOUT);
// 异步预置数
// 输入时钟
// 异步清零
// 加减计数
// 预置数输入
// 进位、借位 ，用于级联
reg [3:0] data_r;
assign DOUT = data_r;

always @(posedge clk, posedge clr, posedge load) begin
if (clr == 1)
data_r <= 0;
else if (load == 1)
data_r <= DIN;
else begin
if (up_down == 1) begin
// 异步清零
// 异步预置数
// 加计数
if (data_r == 4'b1001) begin
data_r <= 4'b0000;
c <= 1;
end else begin
data_r <= data_r + 1;
c <= 0;
end
end else begin
//减计数
if (data_r == 4'b0000) begin
data_r <= 4'b1001;
c <= 1;
end else begin
data_r <= data_r - 1;
c <= 0;
end
end
end
end
endmodule

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