+-------+--------+
buf -->  |  High |  Low   | (Status Word)
         +-------+--------+
         |    Reserved    |
         +----------------+
         |  Destination   |
         +---          ---+
         |                |
         +---          ---+
         |    Address     |
         +----------------+
         |    Source      |
         +---          ---+
         |                |
         +---          ---+
         |    Address     |
         +----------------+
         |    Protocol    |
         +----------------+
         |     Data       |
         +---          ---+
         |    23 - 750    |
         +---          ---+
         |    Decimal     |
         +---          ---+
         |     Words      |
         +---          ---+
         .                .
         .                .
         .                .
         +----------------+