verilog写一个apb从机

下面是一个简单的APB从机的Verilog代码：

module apb_slave (
    input                   PCLK,
    input                   PRESETn,
    input                   PSEL,
    input                   PENABLE,
    input [1:0]             PWRITE,
    input [31:0]            PADDR,
    input [31:0]            PWDATA,
    output [31:0]           PRDATA,
    output                  PREADY,
    output                  PSLVERR
);
 
// 定义状态机的状态
parameter IDLE = 2'b00, ADDRESS = 2'b01, READ = 2'b10, WRITE = 2'b11;
 
// 定义地址存储器
reg [31:0] mem [0:1023];
 
// 定义状态机的各个状态
reg [1:0] state, next_state;
 
// 定义寄存器
reg [31:0] addr_reg, data_reg, read_data;
 
// 定义使能信号
wire enable;
assign enable = (PSEL & PENABLE);
 
// 定义错误信号
wire error;
assign error = 0;
 
// 定义状态机的转移条件
always @(posedge PCLK, negedge PRESETn)
begin
    if (~PRESETn) begin
        state <= IDLE;
    end else begin
        state <= next_state;
    end
end
 
// 定义状态机的状态转移逻辑
always @(*)
begin
    next_state = state;
 
    case (state)
        IDLE:
            if (enable) begin
                next_state = ADDRESS;
                addr_reg <= PADDR;
            end
        ADDRESS:
            if (enable) begin
                if (PWRITE == 2'b00) begin
                    next_state = READ;
                end else begin
                    next_state = WRITE;
                    data_reg <= PWDATA;
                end
            end else begin
                next_state = IDLE;
            end
        READ:
            if (enable) begin
                next_state = IDLE;
            end else begin
                next_state = IDLE;
                read_data <= mem[addr_reg];
            end
        WRITE:
            if (enable) begin
                next_state = IDLE;
            end else begin
                next_state = IDLE;
                mem[addr_reg] <= data_reg;
            end
        default: next_state = IDLE;
    endcase
end
 
// 定义输出
assign PRDATA = (state == READ) ? read_data : 32'h0;
assign PREADY = (state == READ || state == WRITE) ? 1'b1 : 1'b0;
assign PSLVERR = error;
 
endmodule

该代码实现了一个简单的APB从机，包括状态机、地址存储器、寄存器、使能信号、错误信号和输出。你可以根据需要进行修改和扩展。