Low level device interface for direct access storage device including minimum functions and enabling high data rate performance

A low level device interface (LLDI) including minimum functions used between at least one controller and a plurality of devices in a direct access storage device, said LLDI comprising:

• interface means including only a two-wire serial input means and a two-wire serial output means coupled to said controller and said plurality of devices for receiving and for transmitting message information and data information to and between the controller and at least one device in the direct access storage device;
• high speed read logic data function means coupled to said two-wire serial interface means responsive to a received predetermined read data information from the controller for reading and transmitting the requested data from a device to the controller in the direct access storage device;
• high speed write logic data function means coupled to said interface means and responsive to a received predetermined write data information from the controller for transferring and writing the received data from the controller to a device in the direct access storage device;
• and
• means coupled between said interface means and said high speed read and write logic data function means for blocking received message information from received data information, and said message information being transmitted within sand between data information transmissions, said message information being transmitted by both the controller and the devices and said message information being generated by a microprocessor in the LLDI and said message information including a predetermined control bit within each data byte indicating message information, said predetermined control bit identified by said received message information blocking means for blocking received message information from received data information.