APB总线verilog代码示例

以下是一个简单的 APB 总线的 Verilog 代码示例：

module apb_master (
    input clk,
    input rst,
    output reg [31:0] addr,
    output reg [31:0] data_out,
    input [31:0] data_in,
    output reg pwrite,
    output reg penable,
    output reg psel,
    output reg [1:0] psize,
    output reg [1:0] pburst,
    output reg [1:0] pprot,
    output reg [3:0] pstrb
);

reg [31:0] count;

parameter IDLE = 2'b00;
parameter ADDR_PHASE = 2'b01;
parameter DATA_PHASE = 2'b10;
parameter COMPLETE = 2'b11;

reg [1:0] state;

always @(posedge clk or posedge rst) begin
    if (rst) begin
        state <= IDLE;
        addr <= 0;
        pwrite <= 0;
        penable <= 0;
        psel <= 0;
        psize <= 0;
        pburst <= 0;
        pprot <= 0;
        pstrb <= 0;
        count <= 0;
    end else begin
        case (state)
            IDLE: begin
                penable <= 0;
                if (count == 0) begin
                    psel <= 1;
                    psize <= 2'b10;
                    pburst <= 2'b00;
                    pprot <= 2'b000;
                    pstrb <= 4'hF;
                    addr <= {addr[31:2], count};
                    state <= ADDR_PHASE;
                end else begin
                    count <= count - 1;
                end
            end
            ADDR_PHASE: begin
                penable <= 1;
                if (count == 0) begin
                    count <= 3;
                    state <= DATA_PHASE;
                end else begin
                    count <= count - 1;
                end
            end
            DATA_PHASE: begin
                if (count == 0) begin
                    if (pwrite) begin
                        data_out <= data_in;
                    end
                    state <= COMPLETE;
                end else begin
                    count <= count - 1;
                end
            end
            COMPLETE: begin
                penable <= 0;
                psel <= 0;
                psize <= 0;
                pburst <= 0;
                pprot <= 0;
                pstrb <= 0;
                count <= 0;
                state <= IDLE;
            end
        endcase
    end
end

endmodule

这个模块实现了一个 APB 主设备，可以通过这个模块向 APB 总线上的从设备发出读写请求，并接收从设备返回的数据。在这个示例中，APB 主设备的状态机实现了一个简单的读写序列，首先发送地址，然后发送数据，最后接收从设备返回的数据。在实际应用中，APB 主设备的状态机将会更加复杂，以适应更多的读写序列和从设备。