Verilog 4x16解码器输出错误数据
我用Verilog实现了一个4x16解码器,并进行了测试。对于每种情况,解码器都应输出一个16位数字,其中只有一位高。我无法在运行程序时获得所有所需的输出。以下是解码器和测试的代码,以及控制台的输出: 4x16解码器:Verilog 4x16解码器输出错误数据,verilog,decoder,icarus,Verilog,Decoder,Icarus,我用Verilog实现了一个4x16解码器,并进行了测试。对于每种情况,解码器都应输出一个16位数字,其中只有一位高。我无法在运行程序时获得所有所需的输出。以下是解码器和测试的代码,以及控制台的输出: 4x16解码器: module Decoder4x16 (input [3:0] select, input enable, output reg [16:0] out); always @(select, enable) begin if(enable == 1'b0)
module Decoder4x16 (input [3:0] select, input enable, output reg [16:0] out);
always @(select, enable)
begin
if(enable == 1'b0)
out = 16'b0000000000000000;
else if(enable == 1'b1)
if(select == 4'b0000)
out <= 16'b0000000000000001;
else if(select == 4'b0001)
out <= 16'b0000000000000010;
else if(select == 4'b0010)
out <= 16'b0000000000000100;
else if(select == 4'b0011)
out <= 16'b0000000000001000;
else if(select == 4'b0100)
out <= 16'b0000000000010000;
else if(select == 4'b0101)
out <= 16'b0000000000100000;
else if(select == 4'b0110)
out <= 16'b0000000001000000;
else if(select == 4'b0111)
out <= 16'b0000000010000000;
else if(select == 4'b1000)
out <= 16'b0000000100000000;
else if(select == 4'b1001)
out <= 16'b0000001000000000;
else if(select == 4'b1010)
out <= 16'b0000010000000000;
else if(select == 4'b1011)
out <= 16'b0000100000000000;
else if(select == 4'b1100)
out <= 16'b0001000000000000;
else if(select == 4'b1101)
out <= 16'b0010000000000000;
else if(select == 4'b111)
out <= 16'b0100000000000000;
else if(select == 4'b1111)
out <= 16'b1000000000000000;
end
endmodule
当我运行程序时,它输出正确的输出,直到它到达输入为1101的测试用例。在此之后,解码器输出错误的值,它应该显示。以下是输出:
select = 0000 out = 00000000000000001
select = 0001 out = 00000000000000010
select = 0010 out = 00000000000000100
select = 0011 out = 00000000000001000
select = 0100 out = 00000000000010000
select = 0101 out = 00000000000100000
select = 0110 out = 00000000001000000
select = 0111 out = 00000000010000000
select = 1000 out = 00000000100000000
select = 1001 out = 00000001000000000
select = 1010 out = 00000010000000000
select = 1011 out = 00000100000000000
select = 1100 out = 00001000000000000
select = 1101 out = 00010000000000000
select = 1110 out = 00010000000000000
select = 1111 out = 01000000000000000
这里,
out
是一个reg
,这意味着它持有一个分配给它的值。如果select=4'b1110
的条件为else,则不存在else。因此,out
保持它的先前值,该值来自select=4'b1101
。也就是说,out
保存显示的值000100000000000
因此,为select=4'b1110
添加一个else条件,代码正常工作
else if(select == 4'b1110)
out <= 16'b0100000000000000;
还有一件事需要详细说明,请使用始终@(*)
而不是手动灵敏度列表。这将有助于减少敏感度列表的混乱。试试这个简单的代码
module Decoder4x16 (input [3:0] select,
input enable,
output wire [16:0] out);
assign out = {17{enable}} & (1'b1 << select);
endmodule
模块解码器4x16(输入[3:0]选择,
输入使能,
输出线[16:0]输出);
赋值={17{enable}}&(1'b1)您键入了一个条件:else if(select==4'b111)
应该是else if(select==4'b1110)
您能解释一下吗赋值={17{enable}&(1'b1 1被移到select输入给定的十进制位置。
else if(select == 4'b1110)
out = 16'b0100000000000000; // blocking
module Decoder4x16 (input [3:0] select,
input enable,
output wire [16:0] out);
assign out = {17{enable}} & (1'b1 << select);
endmodule