CAN/CSA-ISO/IEC 14776-112-04 (R2017)

Introduction
1 Scope
2 Normative references
3 Definitions, symbols, abbreviations and conventions
4 General
5 SCSI parallel interface connectors
6 SCSI bus interconnect
7 SCSI parallel interface electrical characteristics
8 SCSI bus signals
9 SCSI parallel bus timing
10 Removal and insertion of SCSI devices
11 Logical characteristics
Annex A - Additional requirements for LVD SCSI drivers and
          receivers
Annex B - SCSI configured automatically (SCAM)
Annex C - SCSI bus fairness
Annex D - SCA-2 Connector pinouts
Annex E - Interconnecting buses of different widths
Annex F - Cabling and cable measurement method recommendations
Annex G - Transmission line considerations for fast-20 data
          transfer rates
Annex H - Measuring SE pin capacitance
Annex I - SCSI ICONS
Annex J - Example of HVD terminator network
Annex K - SCSI-3 to SCSI-2 terminology mapping
Annex L - SCA-2 Unshielded Connections
Annex M - VHDCI Shielded Configurations

Specifies the mechanical, electrical, timing, and protocol requirements of the SCSI parallel interface to allow conforming devices to interoperate.

Scope This international standard defines the mechanical, electrical, timing, and protocol requirements of the SCSI parallel interface to allow conforming devices to interoperate. The SCSI parallel interface is a local I/O bus that may be operated over a wide range of transfer 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 devices may be added to the host computers without requiring modifications to generic system hardware. Provision is made for the addition of special features and functions through the use of vendor-specific options. Reserved areas are provided for future standardization. b) To provide compatibility such that properly conforming SCSI-2 devices may interoperate with SCSI-3 devices given that the systems engineering is correctly done. Properly conforming SCSI-2 devices should respond in an acceptable manner to reject SCSI-3 protocol extensions. SCSI-3 protocol extensions are designed to be permissive of such rejections and thus allow the SCSI-2 devices to continue operation without requiring the use of the extension. The interface protocol includes provision for the connection of multiple initiators (SCSI devices capable of initiating an I/O process) and multiple targets (SCSI devices capable of responding to a request to perform an I/O process). Distributed arbitration (i.e., bus-contention logic) is built into the architecture of SCSI. A default priority system awards interface control to the highest priority SCSI device that is contending for use of the bus and an optional fairness algorithm is defined. This Standard defines the physical attributes of an input/output bus for interconnecting computers and peripheral devices.