可以编译通过 下载到板子上就运行不了 为啥？？

有人在吗？？
module flow (
input sys_clk,
input sys_reset,

output reg [7:0] s
);

reg [25:0] clk;
reg [3:0]  count;

always @(posedge sys_clk or negedge sys_reset) begin
        if(sys_reset == 1'b0)begin
                clk = 0;
        end
        else if(clk == 26'd50000000)begin
                clk = 0;
        end
        else begin
                clk = clk + 1;
        end
end

always @(posedge sys_clk or negedge sys_reset) begin
        if(sys_reset == 1'b0)begin
                count = 4'd0;
        end
        else if(clk == 26'd50000000 && count == 4'd9)begin
                count = 4'd0;
        end
        else if(clk == 26'd50000000)begin
                count = count + 1;
        end
end

always @(*) begin
        case(count)
        0: begin s = 8'd0; end
        1: begin s = 8'd1; end
        2: begin s = 8'd2; end
        3: begin s = 8'd4; end
        4: begin s = 8'd8; end
        5: begin s = 8'd16;end
        6: begin s = 8'd32;end
        7: begin s = 8'd64;end
        8: begin s = 8'd128;end
        default :begin s = 8'd0; end
        endcase
end

endmodule
       

可以编译通过
下载到板子上就运行不了
为啥？？