verilog中sum=3’b0 什么意思
时间: 2023-06-27 18:00:53 浏览: 103
在 Verilog 中,3'b0 表示一个 3 位二进制数,其中每一位都是 0。这通常用于初始化一个变量或信号的值为 0。例如,如果我们有一个名为 sum 的 3 位变量,并且我们希望将其初始化为 0,则可以使用以下代码:
```
reg [2:0] sum;
initial begin
sum = 3'b0;
end
```
这将把 sum 的值设置为 000。
相关问题
Verilog 中function 函数用法
在 Verilog 中,function 函数可以用来实现一些简单的逻辑运算或计算,其语法为:
```
function [data_type] function_name ( input [input_type] input_name, ... );
[data_type] variable_name;
// 函数操作
return variable_name;
endfunction
```
其中,`[data_type]` 表示函数返回值的数据类型,`function_name` 是函数的名称,`[input_type]` 表示输入参数的数据类型,`input_name` 是输入参数的名称,`variable_name` 是函数内部定义的变量名称。
下面是一个简单的例子,实现两个 4 位二进制数的加法:
```
function [3:0] adder (input [3:0] a, b);
reg [3:0] sum;
integer i;
sum = 4'b0;
for (i = 0; i < 4; i = i + 1) begin
sum[i] = a[i] + b[i] + sum[i];
if (sum[i] > 1) begin
sum[i+1] = 1;
sum[i] = sum[i] - 2;
end
end
return sum;
endfunction
```
在上面的代码中,`adder` 函数的返回值为一个 4 位二进制数,输入参数为两个 4 位二进制数 `a` 和 `b`。函数内部定义了一个 4 位寄存器 `sum`,并通过 for 循环实现了二进制数的加法运算。最后,函数返回计算结果 `sum`。
在 Verilog 中,function 函数可以在模块内部和模块外部使用。在模块内部使用时,可以直接调用函数名称,如:
```
module top;
reg [3:0] a, b;
wire [3:0] sum;
function [3:0] adder (input [3:0] a, b);
// 函数操作
endfunction
assign sum = adder(a, b);
endmodule
```
在模块外部使用时,需要使用 `extern` 关键字声明函数,并在调用时指定函数名称和参数类型,如:
```
extern function [3:0] adder (input [3:0] a, b);
module top;
reg [3:0] a, b;
wire [3:0] sum;
assign sum = adder(a, b);
endmodule
```
module DW01_add_tb; // Declare inputs and outputs reg [3:0] A; reg [3:0] B; reg CI; wire [3:0] SUM; wire CO; // Instantiate design under test DW01_add dut( .A(A), .B(B), .CI(CI), .SUM(SUM), .CO(CO) ); // Initialize inputs initial begin A = 4'b0000; B = 4'b0000; CI = 0; end // Adder test case task test_adder; // Test case 1: 0 + 0 with carry-in of 0 A = 4'b0000; B = 4'b0000; CI = 0; #10; if (SUM !== 4'b0000 || CO !== 1'b0) $display("Test failed! 0 + 0 should be 0 with carry-out of 0"); // Test case 2: 7 + 3 with carry-in of 0 A = 4'b0111; B = 4'b0011; CI = 0; #10; if (SUM !== 4'b1010 || CO !== 1'b0) $display("Test failed! 7 + 3 should be 10 with carry-out of 0"); // Test case 3: 5 + 11 with carry-in of 1 A = 4'b0101; B = 4'b1011; CI = 1; #10; if (SUM !== 4'b0001 || CO !== 1'b1) $display("Test failed! 5 + 11 should be 16 with carry-out of 1"); // Test case 4: 15+15 with carry-in of 1 A = 4'b1111; B = 4'b1111; CI = 1; #10; if (SUM !== 4'b1110 || CO !== 1'b1) $display("Overflow!!!"); endtask // Run test cases initial begin test_adder(); $finish; end endmodule // DW01_add_tb If I want to replace the delays, i.e, #10; in this piece of verilog code, by below code: integer cyc; initial cyc=1; always @ (posedge clk) begin cyc <= cyc+1; if(cyc==1)begin in_val1 <=4'd4; end else if (cyc==2) begin if (out_val1 !==8'b1) $stop; in_val <=4'd3; end else if (cyc==3)begin if(out_val1 !== 8'b10)$stop; in_val1 <= 4'd7; end else if(cyc==4) begin $write("ALL Finished \n"); $finish; end end in other words, using pound delay # is not allowed, how should I modify the code?
To replace the delays with the code you provided, you can use a counter to keep track of the number of clock cycles and use an if-else statement to control the input values at each cycle. Here's an example:
```
module DW01_add_tb;
// Declare inputs and outputs
reg [3:0] in_val1;
reg [3:0] in_val2;
wire [3:0] out_sum;
wire out_carry;
// Instantiate design under test
DW01_add dut(
.A(in_val1),
.B(in_val2),
.SUM(out_sum),
.CO(out_carry)
);
// Initialize inputs
initial begin
in_val1 = 4'b0000;
in_val2 = 4'b0000;
end
// Clock generator
reg clk = 0;
always #5 clk = ~clk;
// Counter to keep track of clock cycles
integer cyc = 0;
// Control input values without using pound delay #
always @(posedge clk) begin
cyc <= cyc + 1;
if (cyc == 1) begin
in_val1 <= 4'd4;
end else if (cyc == 2) begin
if (out_sum !== 4'b0001 || out_carry !== 1'b0) $stop;
in_val1 <= 4'd3;
end else if (cyc == 3) begin
if (out_sum !== 4'b0111 || out_carry !== 1'b0) $stop;
in_val1 <= 4'd7;
in_val2 <= 4'd5;
end else if (cyc == 4) begin
if (out_sum !== 4'b0000 || out_carry !== 1'b1) $stop;
in_val1 <= 4'd15;
in_val2 <= 4'd15;
end else if (cyc == 5) begin
if (out_sum !== 4'b1110 || out_carry !== 1'b1) $stop;
$write("ALL Finished\n");
$finish;
end
end
endmodule // DW01_add_tb
```
In this code, the clock generator generates a clock signal with a period of 10 time units (5 time units high, 5 time units low). The counter `cyc` keeps track of the number of clock cycles and is incremented on each positive edge of the clock. The if-else statement controls the input values at each clock cycle based on the value of `cyc`, and the output values are checked using an assertion. Finally, when all the test cases are completed, the simulation is finished using `$finish`.