SCSI interface employing bus extender and auxiliary bus

In an interface for interconnecting for communication a digital computer with a plurality of peripheral devices employing an addressing scheme including an address-identifying code (ID) field and an address-descriptor field, and including a main bus to which said computer is connected, and an auxiliary bus to which said peripheral devices are connected, a bus extender for interconnecting said main and auxiliary buses;

• each of said computer and said bus extender having a corresponding main-bus ID and each of said peripheral devices and said bus extender having a corresponding auxiliary-bus ID;
• said bus extender comprising
• A) a main-bus transceiver connected to said main bus for receiving therefrom a plurality of connection-control signals and a plurality of message signals, said connection-control signals having first address fields each providing an ID of a target, and second address fields each providing an address descriptor;
• B) logic means coupled to said main-bus transceiver for identifying connection-control signals having said extender main-bus ID in said first address fields, said logic means including
• i) means for converting data included in the second address fields of the identified connection-control signals into corresponding auxiliary-bus ID's, and
• ii) means coupled with said converting means for forming modified connection-control signals having said auxiliary-bus ID's in the first address field's;
• and
• C) an auxiliary-bus transceiver coupled to said logic means for transmitting said modified connection-control signals on said auxiliary bus for establishing communication with the peripheral devices on said auxiliary bus identified by the auxiliary-bus ID's in the first address fields of the modified connection-control signals, and, upon communication being established, for transmitting message signals received by said main-bus transceiver directly onto said auxiliary bus.

An interface for interconnecting for communication a digital computer with a plurality of peripheral devices, said interface comprising a main bus to which said computer is connected, an auxiliary bus to which said peripheral devices are connected, and a bus extender for interconnecting said main and auxiliary buses;

• said interface employing an addressing scheme including an address-identifying code (ID) field and an address-descriptor field, each of said computer and said bus extender having a corresponding main-bus ID and each of said peripheral devices and said extender having a corresponding auxiliary-bus ID;
• said interface establishing communication between said computer and said peripheral devices using connection-control signals having a first address field providing the ID of a target and a second address field providing an address descriptor, said bus extender comprising
• A) a main-bus transceiver connected to said main bus for receiving therefrom said connection-control signals and a plurality of message signals;
• B) logic means coupled to said main-bus transceiver for identifying connection-control signals having said extender-main-bus ID as a target ID, said logic means including
• i) means for converting data included in the address-descriptor fields of the identified connection-control signals into auxiliary-bus ID's, and
• ii) means coupled with the converting means for forming modified connection-control signals having said auxiliary-bus ID's in the first address fields;
• C) an auxiliary-bus transceiver coupled to said logic means for transmitting said modified connection-control signals on said auxiliary bus for establishing communication with the peripheral devices on said auxiliary bus identified by the auxiliary-bus ID's specified as the target ID's by the modified connection-control signals, and, upon communication being established, for transmitting message signals received by said main-bus transceiver directly onto said auxiliary bus.

A bus extender for connecting a single port of on a first bus to a single port on a second bus so as to interconnect one or more first devices connected to said first bus to one or more second devices connected to said second bus, said bus extender comprising:

• A) first-bus receiving means coupled to said first bus for receiving a plurality of first connection control signals and a plurality of first message data signals over said first bus, each of said first message data signals corresponding to at least one of said first connection control signals, a plurality of said first connection control signals including a plurality of first fields each representing a first-bus target identifier corresponding to said bus extender, and a plurality of second fields each representing a second-bus ultimate target identifier corresponding to one of said second devices connected to said second bus, said plurality of said first connection control signals thereby comprising extender first connection control signals;
• B) second-bus driver means coupled to said second bus for sending a plurality of second connection control signals and a plurality of second message data signals over said second bus to said second devices, each said second message data signal corresponding to at least one of said second connection control signals;
• C) first logic means coupled with said first-bus receiving means for generating said second connection control signals in response to said extender first connection control signals, said second connection control signals having a plurality of third fields each representing a second-bus target identifier corresponding to said second-bus ultimate target identifier of a corresponding one of said first connection control signals, and having a plurality of fourth fields each representing a second-bus source identifier corresponding to said bus extender;
• and
• D) first transfer means coupled with said first logic means and said second-bus driver means for providing said second connection control signals and said corresponding second message data signals to said second bus.

A method of operating a bus extender that interconnects a first bus and a second bus for communication between a first device connected to said first bus and a second device connected to said second bus, said bus extender having a first ID on said first bus and a second ID on said second bus, said method comprising the steps of:

• A) monitoring a plurality of target ID fields of a plurality of first connection control signals received over said first bus to identify those first connection control signals containing said first ID, thereby indicating that said bus extender is a designated recipient thereof,
• B) in response to said first connection control signals identified in step (A),
• (1) generating a plurality of initiator ID's from data in a plurality of initiator ID fields of said first connection control signals so as to identify an initiator for each said first connection control signal, and establishing communication link for each over said first bus with said identified initiator;
• (2) arbitrating for control of a second bus;
• (3) translating data contained in a plurality of descriptor fields of said first connection control signals into a plurality of target ID's on said second bus;
• (4) generating a plurality of second connection control signals corresponding to said first connection control signals, said second connection control signal representing said target ID's on said second bus in a plurality of target ID fields, and said second ID's in a plurality of initiator fields;
• (5) sending said second connection control signals over said second bus to establish for each a communication link with a target identified by said target ID.