     Data Bus        |Read/Write|
    +---------------+------------------+-----------------------+----------+
    |           1   |  PBR,PC          | Op Code               |    R     |
    |           2   |  PBR,PC+1        | Direct Offset         |    R     |
    |       (2) 2a  |  PBR,PC+1        | Internal Operation    |    R     |
    |           3   |  0,D+DO          | Absolute Address Low  |    R     |
    |           4   |  0,D+DO+1        | Absolute Address High |    R     |
    |           5   | 