Secondary storage facility employing serial communications between drive and controller

Claim 1

A secondary storage system for a data processing system, said secondary storage system comprising a mass storage device, a controller for effectuating operations of the device, and an apparatus for establishing a communications path between the controller and device, said apparatus for establishing a communications path being capable of communicating command, response, data and status information on only four unidirectional channels, whereas similar information is normally communicated between a device and controller on more than four unidirectional channels by a standard apparatus for establishing a communication path, said apparatus comprising: a radial bus, comprising substantially only first and second unidirectional channels for carrying signals from said controller to said device and third and fourth unidirectional channels for carrying signals from said device to said controller; means associated with the controller for generating and applying to the first channel and means associated with the device for receiving from the first channel, a continuous transmission of sequences of bit-multiplexed, bit-serial, real-time, signals, each of said sequences being indicative of a set of status variables that define the state of the controller; means associated with the controller for generating and applying to the second channel and means associated with the device for receiving from the second channel, bit-serial command messages and write data; means associated with the device for generating and applying to the third channel and means associated with the controller for receiving from the third channel, a continuous transmission of sequences of bit-multiplexed, bit-serial, real-time signals, each of said sequences being indicative of a set of status variables that define the state of the device; means associated with the device for generating and applying to the fourth channel and means associated with the controller for receiving from the fourth channel, bit-serial response messages and read data; means associated with the controller, responsive to said sequences of signals indicative of a set of status variables of the device an responsive to said response messages and read data, for effectuating the operation of said controller; means associated with the device, responsive to said sequence of signals indicative of a set of status variables of the controller and responsive to said command messages and write data, for effectuating the operation of said device; and wherein each of said sequence indicative of the state of the mass storage device is a bit pattern and wherein within said bit pattern indicative of the state of the device, A. a predetermined first bit provides a synchronization bit; B. a predetermined second bit provides a receiver ready signal; C. a predetermined third bit provides an attention signal; D. a predetermined fourth bit provides a read/write ready signal; E. a predetermined fifth bit provides a sector pulse signal; and F. a predetermined sixth bit provides an available status signal.