Verilog case
时间: 2023-06-28 11:15:14 浏览: 144
Verilog中的case语句是一种控制结构,用于根据输入值执行不同的操作。它类似于C语言中的switch语句。
下面是一个简单的Verilog case语句的示例:
```verilog
module example(input [1:0] sel, output reg [3:0] out);
always @(sel) begin
case(sel)
2'b00: out = 4'b0000;
2'b01: out = 4'b0001;
2'b10: out = 4'b0010;
2'b11: out = 4'b0011;
default: out = 4'bXXXX;
endcase
end
endmodule
```
在这个例子中,输入sel是一个2位二进制数字,输出out是一个4位二进制数字。根据输入sel的值,case语句将out赋值为不同的值。如果输入sel的值与任何一个case标签都不匹配,则执行default标签。
请注意,case语句是一个阻塞式的结构,它会在每次输入sel发生变化时执行。在这个例子中,always块的敏感列表包括sel,因此当输入sel发生变化时,case语句将重新执行,并根据新的输入sel值更新输出out。
相关问题
verilog case
Verilog `case`语句是一种多路分支语句,用于根据不同的条件执行不同的操作。语法如下:
```
case (expression)
case_value_1: statement_1;
case_value_2: statement_2;
...
default: default_statement;
endcase
```
其中,`expression`是一个变量或表达式,`case_value_1`、`case_value_2`等是不同的取值,`statement_1`、`statement_2`等是与相应取值对应的操作语句,`default_statement`是当`expression`的值与所有`case_value`不匹配时执行的语句。
例如,以下代码演示了如何使用`case`语句实现一个简单的状态机:
```
module fsm (
input clk,
input reset,
input [1:0] input_value,
output [1:0] state
);
reg [1:0] current_state;
always @(posedge clk or posedge reset) begin
if (reset) begin
current_state <= 2'b00;
end else begin
case (current_state)
2'b00: begin
if (input_value == 2'b00) begin
current_state <= 2'b00;
end else begin
current_state <= 2'b01;
end
end
2'b01: begin
if (input_value == 2'b01) begin
current_state <= 2'b10;
end else begin
current_state <= 2'b00;
end
end
2'b10: begin
if (input_value == 2'b10) begin
current_state <= 2'b00;
end else begin
current_state <= 2'b01;
end
end
default: current_state <= 2'b00;
endcase
end
end
assign state = current_state;
endmodule
```
在这个例子中,`input_value`可以取`2'b00`、`2'b01`或`2'b10`三种值。根据`current_state`的取值,可以确定下一个状态和输出值。例如,当`current_state`为`2'b00`且`input_value`为`2'b01`时,下一个状态为`2'b01`,输出值为`2'b00`。当`current_state`为`2'b01`且`input_value`为`2'b01`时,下一个状态为`2'b10`,输出值为`2'b01`。当`current_state`不匹配任何一个`case_value`时,执行`default`语句,将`current_state`赋值为`2'b00`。
Verilog case
In Verilog, the "case" statement is used for conditional branching. It allows the programmer to specify multiple conditions and corresponding actions to be taken based on the evaluation of these conditions. The syntax of the "case" statement is as follows:
```
case (expression)
value1: action1;
value2: action2;
...
default: default_action;
endcase
```
Here, "expression" is the variable or expression to be evaluated, and "value1", "value2", etc. are the possible values that the expression can take. For each value, there is a corresponding action to be taken, specified by "action1", "action2", etc. The "default" keyword is used to specify the action to be taken when none of the other values match the expression.
For example, the following Verilog code uses a "case" statement to implement a simple multiplexer:
```
module mux(input sel, input in0, input in1, output reg out);
always @ (sel, in0, in1)
case (sel)
1'b0: out = in0;
1'b1: out = in1;
default: out = 1'b0; // default action
endcase
endmodule
```
Here, the "sel" input determines which input to pass through to the output "out". If "sel" is 0, then "in0" is passed through, and if "sel" is 1, then "in1" is passed through. The "default" action sets "out" to 0 if none of the other cases match.
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