要求根据cyclone IV E 的FPGA实验板功能，设计四位数码管显示的数字时钟；要求：数字时钟能够准确计时并显示；开机显示00；具备控制功能按键有3个：清零、暂停、计时开始。数码管接口:DIG1,DIG2,DIG3,DIG4,SEG0,SEG1,SEG2,SEG3,SEG4,SEG5,SEG6,SEG7,根据对应的四位数码管接口，给出Verilog代码

根据您的要求，以下是一个简单的Verilog代码示例。请注意，这只是一个示例，您可能需要根据您的具体要求进行一些修改或调整。

module digital_clock (
    input clock,
    input reset,
    input clear,
    input pause,
    input start,
    output reg [3:0] DIG1,
    output reg [3:0] DIG2,
    output reg [3:0] DIG3,
    output reg [3:0] DIG4,
    output reg [7:0] SEG0,
    output reg [7:0] SEG1,
    output reg [7:0] SEG2,
    output reg [7:0] SEG3,
    output reg [7:0] SEG4,
    output reg [7:0] SEG5,
    output reg [7:0] SEG6,
    output reg [7:0] SEG7
);

reg [25:0] counter;
reg [3:0] dig1_val;
reg [3:0] dig2_val;
reg [3:0] dig3_val;
reg [3:0] dig4_val;

always @(posedge clock or posedge reset) begin
    if (reset) begin
        counter <= 0;
        dig1_val <= 0;
        dig2_val <= 0;
        dig3_val <= 0;
        dig4_val <= 0;
    end else if (pause) begin
        // do nothing
    end else if (start) begin
        counter <= counter + 1;
        if (counter == 1000000) begin
            counter <= 0;
            dig1_val <= dig1_val + 1;
            if (dig1_val == 10) begin
                dig1_val <= 0;
                dig2_val <= dig2_val + 1;
                if (dig2_val == 10) begin
                    dig2_val <= 0;
                    dig3_val <= dig3_val + 1;
                    if (dig3_val == 10) begin
                        dig3_val <= 0;
                        dig4_val <= dig4_val + 1;
                        if (dig4_val == 10) begin
                            dig4_val <= 0;
                        end
                    end
                end
            end
        end
    end else if (clear) begin
        dig1_val <= 0;
        dig2_val <= 0;
        dig3_val <= 0;
        dig4_val <= 0;
    end
end

assign SEG0 = 8'b11000000; // 0
assign SEG1 = 8'b11111001; // 1
assign SEG2 = 8'b10100100; // 2
assign SEG3 = 8'b10110000; // 3
assign SEG4 = 8'b10011001; // 4
assign SEG5 = 8'b10010010; // 5
assign SEG6 = 8'b10000010; // 6
assign SEG7 = 8'b11111000; // 7

always @(posedge clock) begin
    case (counter[23:20])
        4'b0000: begin DIG1 = SEG0; end
        4'b0001: begin DIG1 = SEG1; end
        4'b0010: begin DIG1 = SEG2; end
        4'b0011: begin DIG1 = SEG3; end
        4'b0100: begin DIG1 = SEG4; end
        4'b0101: begin DIG1 = SEG5; end
        4'b0110: begin DIG1 = SEG6; end
        4'b0111: begin DIG1 = SEG7; end
        4'b1000: begin DIG2 = SEG0; end
        4'b1001: begin DIG2 = SEG1; end
        4'b1010: begin DIG2 = SEG2; end
        4'b1011: begin DIG2 = SEG3; end
        4'b1100: begin DIG2 = SEG4; end
        4'b1101: begin DIG2 = SEG5; end
        4'b1110: begin DIG2 = SEG6; end
        4'b1111: begin DIG2 = SEG7; end
    endcase

    case (counter[19:16])
        4'b0000: begin DIG2 = SEG0; end
        4'b0001: begin DIG2 = SEG1; end
        4'b0010: begin DIG2 = SEG2; end
        4'b0011: begin DIG2 = SEG3; end
        4'b0100: begin DIG2 = SEG4; end
        4'b0101: begin DIG2 = SEG5; end
        4'b0110: begin DIG2 = SEG6; end
        4'b0111: begin DIG2 = SEG7; end
        4'b1000: begin DIG3 = SEG0; end
        4'b1001: begin DIG3 = SEG1; end
        4'b1010: begin DIG3 = SEG2; end
        4'b1011: begin DIG3 = SEG3; end
        4'b1100: begin DIG3 = SEG4; end
        4'b1101: begin DIG3 = SEG5; end
        4'b1110: begin DIG3 = SEG6; end
        4'b1111: begin DIG3 = SEG7; end
    endcase

    case (counter[15:12])
        4'b0000: begin DIG3 = SEG0; end
        4'b0001: begin DIG3 = SEG1; end
        4'b0010: begin DIG3 = SEG2; end
        4'b0011: begin DIG3 = SEG3; end
        4'b0100: begin DIG3 = SEG4; end
        4'b0101: begin DIG3 = SEG5; end
        4'b0110: begin DIG3 = SEG6; end
        4'b0111: begin DIG3 = SEG7; end
        4'b1000: begin DIG4 = SEG0; end
        4'b1001: begin DIG4 = SEG1; end
        4'b1010: begin DIG4 = SEG2; end
        4'b1011: begin DIG4 = SEG3; end
        4'b1100: begin DIG4 = SEG4; end
        4'b1101: begin DIG4 = SEG5; end
        4'b1110: begin DIG4 = SEG6; end
        4'b1111: begin DIG4 = SEG7; end
    endcase

    case (counter[11:8])
        4'b0000: begin DIG4 = SEG0; end
        4'b0001: begin DIG4 = SEG1; end
        4'b0010: begin DIG4 = SEG2; end
        4'b0011: begin DIG4 = SEG3; end
        4'b0100: begin DIG4 = SEG4; end
        4'b0101: begin DIG4 = SEG5; end
        4'b0110: begin DIG4 = SEG6; end
        4'b0111: begin DIG4 = SEG7; end
    endcase
end

endmodule

该代码使用一个计数器来计时，以每秒100万次的频率递增。然后，根据计数器的值，将相应的数字显示在四个数码管上。该代码还包括了一些控制信号，例如清零、暂停和计时开始。