IEEE/ISO/IEC 15205-2000

SBus is a high performance computer I/O interface for connecting integrated circuits and SBus Cards to a computer system motherreboard. This standard defines the mechanical, electrical, environmental, and protocol requirements for the design of SBus Cards and the computer system motherreboard that supports those cards. Every SBus Card shall implement appropriate self-descriptive and initialization firmware using FCode, which is similar to the Forth programming language. The details of this firmware standard are beyond the scope of this standard.1) In addition, other software interfaces may be used for communication with SBus Cards. SBus is intended to provide a high performance I/O bus interface with a small mechanical form factor. The small size, high levels of integration, and low power usage of SBus Cards enable them to be used in laptop computers, compact desktop computers, and other applications requiring similar characteristics. SBus Cards are mounted in a plane parallel to the motherreboard of the computer system, allowing the computer system to have a low profile. SBus is not designed as a general purpose backplane bus. SBus allows transfers to be in units of 8, 16, 32, or 64 bits. Burst transfers are allowed to further improve performance. SBus allows a number of SBus Master devices to arbitrate for access to the bus. The chosen SBus Master provides a 32-bit virtual address which the SBus Controller maps to the selection of the proper SBus Slave and the development of the 28-bit physical address for that Slave. The selected SBus Slave then performs the data transfers requested by the SBus Master. Simple SBus Cards may be designed to operate solely as Slaves on the SBus.



New IEEE Standard - Inactive-Withdrawn. An input/output expansion bus with a 32-or 64-bit width is described in this standard.The SBus is designed for systems requiring a small number of expansion ports.SBus Cards may be connected to a standard SBus Connector mounted on the motherreboard.SBus Devices may also be attached to the SBus directly on the system's motherreboard.The dimensions of the SBus Card are 83.8 mm by 146.7 mm,making the cards appropriate for small computer systems that make extensive use of highly integrated circuits.The SBus Cards are designed to be installed in a plane parallel to the system's motherreboard as mezzanine cards. They are designed to provide connections for devices external to the computer system through an exposed back panel.The form factor is useful in Futurebus+,VMEbus,desktop computers,and similar applications. The SBus has the capability of transferring data at rates up to 168 Mbytes/s,depending on the implementation options selected. SBus Cards may either serve as Masters on the bus,providing all virtual address information as well as the data to be transferred,or they may serve as Slaves on the bus,providing data transfer according to the require- ments of some other SBus Master.The SBus Master for a data transfer is selected by an arbitration process managed by the single SBus Controller on the SBus.The SBus Controller provides a virtual to physical ad- dress translation service.