下面的代码为什么会溢出呢? 仿真出现-1和-15536
本帖最后由 orange-208 于 2012-9-27 10:52 编辑如题
module divider
(
clk, rstn,
Cnt1_data,
Cnt2_data,
Data_Bin
);
input clk, rstn;
input Cnt1_data; //Fs limited to 50MHz
input Cnt2_data; //Fx limited to 60MHz
output Data_Bin;
/*******************************************************/
parameter Freq_50MHz = 26'd50_000_000; //Fs = Freq_50MHz
//Freq_50KHz = 16'd50_000;
/*******************************************************/
reg Cnt1_in, Cnt2_in;//Ns = Cnt1_in, Nx = Cnt2_in
reg Data_out; //Fx = Data_out
reg flag;
always @ ( posedge clk or negedge rstn )
if( !rstn )
begin
flag <= 0;
Cnt1_in <= 16'd0;
Cnt2_in <= 16'd0;
Data_out <= 31'd0;
end
else if( Cnt1_in != 16'd0 && flag == 1'b1 )
begin
Data_out <= ( Cnt2_in * Freq_50MHz ) / Cnt1_in;
end
else
begin
flag <= 1'b1;
Cnt1_in <= Cnt1_data;
Cnt2_in <= Cnt2_data;
end
/**************************************/
assign Data_Bin = Data_out;
/**************************************/
endmodule
testbench文件
`timescale 1 ns/ 1 ns
module divider_vlg_tst();
reg Cnt1_data;
reg Cnt2_data;
reg clk;
reg rstn;
wire Data_Bin;
/*****************************/
divider i1
(
.Cnt1_data(Cnt1_data),
.Cnt2_data(Cnt2_data),
.Data_Bin(Data_Bin),
.clk(clk),
.rstn(rstn)
);
/*****************************/
initial
begin
clk = 0;
rstn = 1;
#10 rstn = 0;
#10 rstn = 1;
end
always #10 clk = ~clk;
/**************************************/
always @ ( posedge clk or negedge rstn )
if( !rstn )
begin
Cnt1_data <= 16'd0;
Cnt2_data <= 16'd0;
end
else
begin
Cnt1_data <= 16'd50_000;
Cnt2_data <= 16'd65_535;
end
/**************************************/
endmodule 问题描述不清楚,楼主自己没经过思考就提问,不好。 wjfblack 发表于 2012-9-27 10:03 static/image/common/back.gif
问题描述不清楚,楼主自己没经过思考就提问,不好。
问题解决了,定义位宽的最高位一般为符号位。
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