verilog中 设 parameter A,则case(A)应该怎么写
时间: 2024-02-24 09:56:49 浏览: 15
在 Verilog 中,如果有一个 parameter A,并且你想要在 case 语句中使用它,你可以这样写:
```
parameter A = 2;
reg [3:0] case_var;
always @ (*)
begin
case (A)
2: case_var = 4'b0001;
3: case_var = 4'b0010;
4: case_var = 4'b0100;
default: case_var = 4'b1000;
endcase
end
```
在这个例子中,我们定义了一个 parameter A,并且使用它来控制 case 语句中的分支。在 always 块中,我们声明了一个 reg 类型的变量 case_var,然后根据 parameter A 的值,在 case 语句中选择不同的分支,并将结果赋值给 case_var。
相关问题
veriloga写一个SPI协议
抱歉,我无法为您提供Verilog-A编写SPI协议的示例,因为Verilog-A是用于建模模拟器件和电路行为的语言,而SPI协议是一种通信协议。您需要使用Verilog或VHDL等硬件描述语言来实现SPI协议。以下是一个简单的Verilog实现,用于控制SPI总线上的一个设备:
module spi_device(
input clk,
input reset,
input [7:0] data_in,
output [7:0] data_out,
output cs_n,
output sck,
output mosi,
input miso
);
reg [7:0] shift_reg;
reg [3:0] shift_count;
reg [7:0] tx_reg;
reg [7:0] rx_reg;
reg tx_done;
reg [1:0] state;
parameter IDLE = 2'b00;
parameter SEND = 2'b01;
parameter RECEIVE = 2'b10;
assign data_out = rx_reg;
assign cs_n = (state == IDLE);
assign mosi = (state == SEND) ? tx_reg[7] : 1'b0;
assign sck = (state == SEND || state == RECEIVE);
always @(posedge clk) begin
if (reset) begin
shift_reg <= 8'h00;
shift_count <= 4'd0;
tx_reg <= 8'h00;
rx_reg <= 8'h00;
tx_done <= 1'b0;
state <= IDLE;
end else begin
case (state)
IDLE: begin
if (!cs_n) begin
tx_reg <= data_in;
shift_reg <= tx_reg;
shift_count <= 4'd7;
tx_done <= 1'b0;
state <= SEND;
end
end
SEND: begin
if (shift_count == 4'd0) begin
tx_done <= 1'b1;
state <= RECEIVE;
end else begin
shift_reg <= {shift_reg[6:0], mosi};
shift_count <= shift_count - 1;
end
end
RECEIVE: begin
if (shift_count == 4'd0) begin
rx_reg <= shift_reg;
state <= IDLE;
end else begin
shift_reg <= {miso, shift_reg[7:1]};
shift_count <= shift_count - 1;
end
end
endcase
end
end
endmodule
该模块包含一个8位数据输入端口和一个8位数据输出端口,以及四个SPI总线控制线(cs_n, sck, mosi和miso)。当cs_n为低电平时,输入数据将被发送到SPI总线上,并等待来自SPI总线的响应。发送和接收过程是通过一个8位移位寄存器和一个4位移位计数器实现的。当发送完成时,该模块将进入接收状态,并且在接收到8位数据后将返回空闲状态。
verilog parameter
Verilog parameters are used to define constants or variables that can be assigned values before the compilation of the Verilog code. They are useful for defining configurable parameters in the design, allowing for flexibility and easy modification.
Parameters can be declared at different levels in a Verilog design hierarchy: module level, block level, or even within procedural blocks like tasks or functions. They are typically defined using the `parameter` keyword followed by the data type and the name of the parameter.
Here's an example of declaring a parameter in Verilog:
```verilog
module MyModule #(parameter WIDTH = 8) (input [WIDTH-1:0] data);
// ...
endmodule
```
In this example, `WIDTH` is a parameter with the default value of 8. It is used to specify the width of the `data` input port. The value of the parameter can be overridden when instantiating the module.
Parameters can also be used within procedural blocks:
```verilog
module MyModule #(parameter WIDTH = 8) (input [WIDTH-1:0] data);
// ...
initial begin
// Use the parameter value within an initial block
$display("WIDTH = %d", WIDTH);
end
endmodule
```
In this case, the value of the `WIDTH` parameter is displayed during simulation.
Overall, Verilog parameters provide a way to make designs more flexible and customizable by allowing users to modify certain values without modifying the actual code.