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Method and apparatus for an enhanced computer system interface
| Details |
Inventors: Gajjar, Kumar; Shah, Kaushik S.; Trang, Duc H.;
Assignee: MTI Technology Corporation (Sunnyvale, CA)
Primary Examiner: Ray; Gopal C.
Assistant Examiner:
Attorney, Agent or Firm: Townsend and Townsend and Crew
An improved interface system based in part on the SCSI standard is provided. A single cable data bus simultaneously transfers several bytes of information between two devices. The interface system transfers multiple-byte commands, messages, status information or data in a single parallel transfer. A microsequencer is provided to permit data transfers across the interface without requiring burdensome attention from a processor in a device involved in the transfer. |
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DETAILED DESCRIPTION It is therefore an object of the present invention to provide an improved interface, based in part on the proposed SCSI-2 standard, by which multiple-byte commands, messages, and/or status information can be transferred in a single parallel transfer.
It is also an object of the present invention to provide a circuit for implementing the protocol of such an improved interface that can execute data transfers with minimal need for the attention of a device processor.
It is another object of the present invention to provide an improved interface that can be implemented using conventional SCSI integrated circuits and other commercially available components.
These and other objects of the invention are accomplished in accordance with the principles of the invention by providing an interface (referred to hereafter as a SCSI-2E interface) comprising, in the preferred embodiment, a bus capable of simultaneously transferring at least 32 bits of data (plus at least 4 bits of parity data), and a microsequencer-driven interface unit for connecting devices to the bus.
A conventional 64-conductor cable has been found to be suitable for implementing the bus of this invention (referred to hereafter as a SCSI-2E cable), although cables of other widths may also be used.
In addition to having data and parity lines for transferring 32 bits of data (and their associated parity bits) in parallel, the SCSI-2E cable includes nine dedicated control lines.
The remaining lines provide paths for terminator power and ground.
The various data, parity, control, and other lines may be arranged within the cable as desired.
The SCSI-2E interface offers several advantages over the prior art.
For example, a single SCSI-2E cable replaces two prior art SCSI-2 cables (i.
e.
, cables A and B).
Also, the SCSI-2 A and B cables require separate "Request" and "Acknowledge" lines for each of the cables.
These two sets of Request and Acknowledge lines are required to synchronize the transfer of data on cables A and B during multiple-byte parallel data transfers
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I/O Systems 
