there are two system interfaces:

    1 one rs-232c serial interface

    2 one parallel centronics interface.

    the interfaces can be operated in three different modes:

    1 serial interface active

    2 parallel interface active

    3 both interfaces active in shared mode

    the following chapter gives an overview about interface characteristics, control signals, protocols, and cabling.

    any change of the operation mode (serial, parallel or shared) and of the size of the interface buffer is possible only when the interface buffer is completely empty of data.

    display messages: ready 4 elq , busy 4 elq, or local.