标准编号：ISO/IEC 14776-115:2004
中文名称：信息技术.小型计算机系统接口（SCSI）.第115部分：平行接口-5（SPI-5）
英文名称：Information technology — Small Computer System Interface (SCSI) — Part 115: Parallel Interface-5 (SPI-5)
发布日期：2004-11
标准范围
This part of ISO/IEC 14776 defines the mechanical, electrical, timing, and protocolrequirements of the SCSI parallel interface to allow conforming SCSI devices to inter-operate.The SCSI parallel interface is a local I/O bus that may be operated over a wide range oftransfer rates. The objectives of the SCSI parallel interface are:a) To provide host computers with device independence within a class of devices. Thus,different disk drives, tape drives, printers, optical media drives, and other SCSIdevices may be added to the host computers without requiring modifications to genericsystem hardware. Provision is made for the addition of special features and functionsthrough the use of vendor-specific options. Reserved areas are provided for futurestandardization.b) To provide compatibility such that conforming SPI-2, SPI-3 devices may interoperatewith SPI-5 devices given that the systems engineering is correctly done. ConformingSPI-2, SPI-3, and SPI-5 devices should respond in an acceptable manner to rejectSPI-5 protocol extensions. SPI-5 protocol extensions are designed to be permissive ofsuch rejections and thus allow SPI-2 and SPI-3 devices to continue operation withoutrequiring the use of the extensions.The interface protocol includes provision for the connection of multiple SCSI initiator ports(i.e., SCSI devices capable of initiating an I/O process) and multiple SCSI target ports (i.e.,SCSI devices capable of responding to a request to perform an I/O process). Distributedarbitration (i.e., bus-contention logic) is built into the architecture of this standard. A defaultpriority system awards interface control to the highest priority SCSI device that is contendingfor use of the bus and an optional fairness algorithm is defined.This standard defines the physical attributes of an input/output bus for interconnectingcomputers and peripheral devices.The set of SCSI standards specifies the interfaces, functions, and operations necessary toensure interoperability between conforming SCSI implementations. This standard is afunctional description. Conforming implementations may employ any design technique thatdoes not violate interoperability.This standard has made obsolete single-ended and multimode signaling alternatives.Implementations that use single-ended or multimode signaling alternatives should referencethe SCSI Parallel Interface-2 standard (ISO/IEC 14776-112).
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