Electrical computers and digital data processing systems: input/ – Input/output data processing – Peripheral configuration
Reexamination Certificate
1999-08-27
2003-04-29
Gaffin, Jeffrey (Department: 2182)
Electrical computers and digital data processing systems: input/
Input/output data processing
Peripheral configuration
C710S010000, C710S104000, C713S001000, C709S221000
Reexamination Certificate
active
06557049
ABSTRACT:
BACKGROUND OF THE INVENTION
In general, the present invention relates to computer storage enclosures containing Fast and Ultra SCSI (up to 40 Mbytes/sec, or MBps), Ultra2 (up to 80 MBps), and Ultra3 SCSI (up to 160 MBps) peripherals; and more particularly, to a new “intelligent” SCSI-compliant computer enclosure module having a control unit for manual or auto-configuration of two independently-operational SCSI buses (also operational as a single-unified SCSI bus), auto-termination circuitry capable of configuring (automatically or manually) the termination mode for each bus, and logic for setting a SCSI ID (i.e., the bit-significant representation of a SCSI address) for each device in communication with the SCSI bus(es).
The widely-used small computer system interface (SCSI) protocol was developed for industry groups, under the American National Standards Institute (ANSI) and International Standards Organization (ISO) guidelines, to provide an efficient peer-to-peer I/O bus. A main objective of the standardized protocol adopted for SCSI parallel interface is to provide host computers with device independence within a class of devices. Devices that conform with the mechanical, electrical, timing, and protocol requirements (including the physical attributes of I/O buses used to interconnect computers and peripheral devices) of the SCSI parallel interface will inter-operate. This allows several different peripherals (hard disk drives, removable disk drives, tape drives, CD-ROM drives, printers, scanners, optical media drives, and so on) to be added at the same time to a host computer without requiring modifications to the generic system hardware. For example, personal computers (PC's or microcomputers), are inexpensive yet powerful enough to handle computationally-intensive user applications. The data storage and data sharing capabilities of PC's are often expanded by externally coupling in a cluster environment, using SCSI protocol, as many as two such computers to a group of peripheral devices such as disk drives, tape drives, printers, and scanners. Capacity on a single SCSI bus is limited to 16: The host adapter of a SCSI controller takes up one slot in a PC (and, thus, only one IRQ) but can control up to 15 peripheral devices therefrom.
The working draft of the SCSI Parallel Interface-2 Standard (SPI-2), as modified, defines the cables, connectors, signals, transceivers, and protocol used to interconnect SCSI devices. The SPI-2 working draft states that a SCSI bus consists of all the conductors and connectors required to attain signal line continuity between every driver, receiver, and terminator for each signal. In operation, a SCSI bus is a bidirectional, multimaster bus which can accommodate peer to peer communications among multiple computer processing units (CPUs) and multiple peripheral devices. A SCSI device is a device (any computer peripheral) containing at least one SCSI port and the means to connect the drivers and receivers to the bus. SCSI bus termination is required at each end of a SCSI bus (and, thereby, defines an “end” of any SCSI bus) to set the negation state when no device is driving (this is called “biasing”) and to match the impedance to that of the interconnect media. SCSI signal lines must be terminated at both ends with a terminator compatible with the type/protocol of transceivers (currently defined signal transmission mode protocols include SE/LVD or HVD) used in any connected SCSI device. A termination circuit that is delivering the performance requirements for such biasing and impedance matching is considered “enabled”. A switchable terminator is one that can be “disabled” by disconnecting signal lines. The electrical connection directly between two terminators forms a bus path. Improper termination of a SCSI bus will very likely cause device malfunction. Any electrical path that is not part of the bus-path is a stub. The point where a stub meets the bus path is called a stub connection.
A SCSI primary bus is one that provides for and carries 8-bit or 16-bit data transfer. A SCSI secondary bus carries an additional 16-bit data bus that, when used in conjunction with a 16-bit primary bus, provides for a 32-bit data transfer path (although the latter is not, yet, widely used). SCSI devices may connect to a bus via 8-bit, 16-bit, or 32-bit ports. To date, SCSI parallel interface devices may be implemented with either 50, 68, or 80 pin connectors (whether shielded or unshielded). Eight-bit devices are referred to as “narrow” devices (carried by 50 pin cables and connectors) and devices which permit parallel transfer of 16-bits or 32-bits at a time are called “wide” devices (carried by cables and connectors with at least 68 pin). Narrow and wide, as used in connection with SCSI compliant systems, refers to width of the data path. Data travels fast over SCSI buses, with Ultra SCSI data transfer speeds up to 40 MBps, wide Ultra2 LVD up to 80 MBps, and wide Ultra3 up to 160 MBps. Active termination of the “high byte” must be accomplished if one is to connect a wide (16- or 32-bit transfer using 68 or more pin cable/connector) device to a narrow cable or device (8-bit transfer using 50 pins). As it is well known, a typical data transfer operation over a SCSI bus between a SCSI controller (or “host adapter”) located in a host computer system, to a target device (such as a disk drive) has seven SCSI “phases”: (1) ARBITRATION, (2) SELECTION, (3) RESELECTION, (4) COMMAND, (5) DATA, (6) STATUS and (7) MESSAGE. For example, during the COMMAND phase, a SCSI command is transferred from the host adapter to a target (drive); and so on. Host adapter functional circuitry is typically maintained on a host bus adapter (HBA) chip on a printed circuit board structure referred to as a host adapter board (HAB) for connection to a PC host via an expansion slot. California based Adaptec, Inc., as well as the assignee hereof, design and distribute host adapters for making narrow to wide SCSI connections.
There is a patented ‘one chip bus master host adapter integrated circuit’ specifically designed for (i) connecting a first bus having a specified protocol for transferring information over the first bus and a first data transfer speed to a second bus having a specified protocol for transferring information over the second bus and a second data transfer speed, and (ii) transferring information between the two buses. This bus master host adapter integrated circuit (referred to in the patent as simply a ‘host adapter’) includes a reduced instruction set computing (RISC) processor which controls operations allowing the host adapter to function as a high speed bus master. The patented host adapter includes many features found in traditional add-in card SCSI host adapters: Bus master transfers, fast/wide SCSI, one interrupt per command, scatter/gather, overlapped seeks, tagged queuing, etc.
Transceivers transmit and receive electrical signals/information on a SCSI bus using single-ended (SE) signal transmission mode protocol or a differential protocol (either high voltage differential, HVD, or low voltage differential, LVD). Since the SE and HVD alternatives are mutually exclusive and the LVD and HVD alternatives are mutually exclusive, a bus can support only all HVD devices or SE/LVD signal transmission devices. In addition to SE, LVD, HVD transceivers and terminators, SE/LVD multimode transceiver and multimode terminator architecture has been designed for operation over a SCSI bus in the event it's expected that a combination of SE and LVD protocol devices will be combined thereon. The SE/LVD multimode architecture allows for either SE- or LVD-mode signals depending upon input information sensed regarding respective mode operation via DIFFSENS. Since damage can occur to a SCSI device if a HVD device is plugged into a bus containing a SE/LVD multimode transceiver, or either an SE or LVD transceiver, signal line and interconnect media protocol used over, as well as termination at the end of, each SCSI bus must be appropriately configured. In a standardized SCSI con
Kimminau Michael Darrell
Maloy Joseph M.
Soulier Paul Ernest
Gaffin Jeffrey
Lathrop & Gage
LSI Logic Corporation
Mai Rijue
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