ISO/IEC 14776-113:2002 PDF

Overview

ISO/IEC 14776-113:2002 (SCSI Parallel Interface-3, or SPI-3) is the international standard that defines the mechanical, electrical, timing and protocol requirements for the parallel Small Computer System Interface (SCSI) bus. SPI-3 specifies the physical I/O bus attributes, signal definitions, connectors, cabling, termination and protocol behaviors so that conforming SCSI devices (initiators and targets) can interoperate across a wide range of transfer rates.

Key topics and requirements

• Mechanical and connector definitions - pin assignments and approved shielded/non‑shielded connector alternatives for SPI-3 implementations.
• Electrical characteristics - single‑ended (SE), low voltage differential (LVD) and multimode transceiver behaviors, termination and TERMPWR considerations.
• Bus interconnect and cabling - impedance, conductor size, capacitance, stub length and propagation time/ skew requirements to support high-speed transfers.
• Timing and signal specifications - transmit/receive setup and hold, arbitration timing, REQ/ACK periods, physical disconnection and reset timing, and measurement points for compliance testing.
• Protocol and bus phases - definition of bus phases (BUS FREE, ARBITRATION, SELECTION, DATA, etc.), data transfer modes (ST, DT), pCRC handling and QAS (Quick Arbitration and Selection) behavior.
• Multi-initiator/multi-target architecture - distributed arbitration (bus-contention logic) with a default priority system and an optional fairness algorithm to manage bus ownership.
• Backward compatibility and obsolescence - SPI-3 is designed to interoperate with SCSI-2 / SPI-2 devices when protocol extensions are rejected; SPI-3 explicitly obsoletes some SPI-2 options (e.g., HVD option, 32-bit bus width, SCAM, and certain messages) and directs implementers to ISO/IEC 14776-112 for those features.

Practical applications and users

Who benefits from ISO/IEC 14776-113:

• Hardware designers and device manufacturers building SCSI disk drives, tape drives, optical drives, printers and host adapters.
• System integrators and embedded systems engineers implementing SCSI parallel interfaces and cabling topologies.
• Test and compliance labs validating electrical, timing and protocol conformance for SPI-3 devices.
• Firmware and driver developers implementing SCSI initiator and target behaviors (arbitration, selection, REQ/ACK handshakes).

Practical uses:

• Ensuring interoperability across multi-vendor SCSI ecosystems.
• Designing reliable high-speed parallel I/O links with correct termination and timing margins.
• Creating test plans for electrical and protocol conformance.

Related standards

• ISO/IEC 14776-112 (SCSI Parallel Interface-2 / SPI-2) - referenced for HVD, 32-bit bus width, SCAM and other obsoleted options.
• Other ISO/IEC SCSI family documents covering command sets and system-level SCSI behavior.

Keywords: ISO/IEC 14776-113:2002, SPI-3, SCSI parallel interface, LVD, SE, bus timing, connectors, arbitration, SCSI devices, SCSI standard.