嵌入式网口TX灯闪，PC网口接收灯也闪，但显示接收0字节

嵌入式以太网，发送代码如下：

when Copy01=> --destination mac address ffff ffff ffff

     HD<=X"FFFFFFFF";

    when Copy02=>

     HD<=X"1111FFFF"; -- source mac address 1111 1111 1111

    when Copy03=>

     HD<=X"11111111";

    when Copy04=>

     HD<=X"00450008"; --type IP, IPv4=0100 ,

    when Copy05=>

     HD<=X"00004800";--package size 72 bytes total

    when Copy06=>

     HD<=X"00001140";     

    when Copy07=>

     HD<=X"CC01A8C0"; --source ip 192.168.1.204

    when Copy08=>

     HD<=X"FFFFFFFF";  --destination ip address

    when Copy09=>

     HD<=X"70177017";  -- port number

    when Copy10=>

     HD<=X"00001c00";--  28 bytes data

    when Copy11=>

     HD<=X"11111111";     

    when Copy12=>

     HD<=X"1111FFFF";

    when Copy13=>

     HD<=X"11111111";

    when Copy14=>

     HD<=X"11111111";

    when Copy15=>

     HD<=X"FFFFFFFF";

    when Copy16=>

     HD<=X"1111FFFF";

    when Copy17=>

     HD<=X"11111111";     

    when Copy18=>

     HD<=X"1111FFFF";

    when Copy19=>

     HD<=X"11111111";

实际上就发送了一个很小的IP帧。