写一个FPGA的PCIE接口测试用例

下面是一个简单的FPGA的PCIE接口测试用例，用于测试PCIE Gen2 x1接口。这个例子使用Verilog语言编写。

module pcie_test(
    input clk,
    input reset,
    input [31:0] write_data,
    output [31:0] read_data,
    output reg ready,
    input valid,
    input [31:0] ack
);

reg [31:0] write_data_reg;
reg [31:0] read_data_reg;
reg [31:0] ack_reg;
reg [1:0] state;
reg [31:0] count;

parameter PCIE_BASE_ADDR = 32'h80000000;
parameter PCIE_SIZE = 32'h10000000; // 256MB

always @(posedge clk) begin
    if (reset) begin
        state <= 2'b00;
        read_data_reg <= 0;
        ack_reg <= 0;
        count <= 0;
        ready <= 1'b1;
    end else begin
        case (state)
            2'b00: begin // IDLE
                if (valid) begin
                    state <= 2'b01;
                    count <= 0;
                    ready <= 1'b0;
                end
            end
            2'b01: begin // WRITE ADDRESS
                ack_reg <= ack;
                if (ack_reg) begin
                    state <= 2'b10;
                end
            end
            2'b10: begin // WRITE DATA
                count <= count + 1;
                if (count == 255) begin
                    state <= 2'b11;
                    count <= 0;
                end
            end
            2'b11: begin // READ DATA
                read_data_reg <= #10 {pcie[PCIE_BASE_ADDR + count], pcie[PCIE_BASE_ADDR + count + 1], pcie[PCIE_BASE_ADDR + count + 2], pcie[PCIE_BASE_ADDR + count + 3]};
                count <= count + 4;
                if (count == 1023) begin
                    state <= 2'b00;
                    count <= 0;
                    ready <= 1'b1;
                end
            end
        endcase
    end
end

assign write_data_reg = write_data;
assign read_data = read_data_reg;

// PCIE core instance
pcie_core pcie_inst (
    .clk(clk),
    .reset(reset),
    .pcie_rx_data(bus_rx_data),
    .pcie_rx_valid(bus_rx_valid),
    .pcie_tx_ready(bus_tx_ready),
    .pcie_tx_data(bus_tx_data),
    .pcie_tx_valid(bus_tx_valid),
    .pcie_tx_last(bus_tx_last),
    .pcie_tx_read_enable(bus_tx_read_enable),
    .pcie_tx_write_enable(bus_tx_write_enable),
    .pcie_tx_address(bus_tx_address),
    .pcie_tx_length(bus_tx_length),
    .pcie_tx_count(bus_tx_count),
    .pcie_tx_end(bus_tx_end),
    .pcie_rx_read_data(bus_rx_read_data),
    .pcie_rx_write_data(bus_rx_write_data),
    .pcie_rx_read_address(bus_rx_read_address),
    .pcie_rx_write_address(bus_rx_write_address),
    .pcie_rx_read_enable(bus_rx_read_enable),
    .pcie_rx_write_enable(bus_rx_write_enable)
);

// PCIE memory map
memory_bus #(
    .SIZE(PCIE_SIZE)
) pcie (
    .clk(clk),
    .reset(reset),
    .address(pcie_address),
    .write_data(pcie_write_data),
    .read_data(pcie_read_data),
    .write_enable(pcie_write_enable),
    .read_enable(pcie_read_enable)
);

// PCIE bus interface
bus_interface #(
    .DATA_WIDTH(32),
    .ADDR_WIDTH(32),
    .BURST_LENGTH(256)
) pcie_bus (
    .clk(clk),
    .reset(reset),
    .bus_rx_data(bus_rx_data),
    .bus_rx_valid(bus_rx_valid),
    .bus_tx_ready(bus_tx_ready),
    .bus_tx_data(bus_tx_data),
    .bus_tx_valid(bus_tx_valid),
    .bus_tx_last(bus_tx_last),
    .bus_tx_read_enable(bus_tx_read_enable),
    .bus_tx_write_enable(bus_tx_write_enable),
    .bus_tx_address(bus_tx_address),
    .bus_tx_length(bus_tx_length),
    .bus_tx_count(bus_tx_count),
    .bus_tx_end(bus_tx_end),
    .bus_rx_read_data(bus_rx_read_data),
    .bus_rx_write_data(bus_rx_write_data),
    .bus_rx_read_address(bus_rx_read_address),
    .bus_rx_write_address(bus_rx_write_address),
    .bus_rx_read_enable(bus_rx_read_enable),
    .bus_rx_write_enable(bus_rx_write_enable),
    .bus_address(pcie_address),
    .bus_write_data(pcie_write_data),
    .bus_read_data(pcie_read_data),
    .bus_write_enable(pcie_write_enable),
    .bus_read_enable(pcie_read_enable)
);

endmodule

这个例子中，我们使用了一个状态机来控制PCIE接口的读写操作。当valid信号为高电平时，我们将进入写地址状态，等待ack信号的到来；当ack信号到来时，我们进入写数据状态，每次写入256个字节的数据；当写入完成后，我们进入读数据状态，每次读取1024个字节的数据，并在读取完成后回到IDLE状态。我们同时实例化了一个PCIE核，用于处理PCIE接口的数据收发，以及一个内存映射模块和一个总线接口模块，用于实现对PCIE地址空间的读写操作。

这个例子只是一个简单的FPGA的PCIE接口测试用例，实际应用中需要根据具体的需求进行优化和完善。