The overall level of performance that may be achieved by any computer system is determined, in large part, by the system bus that is used to effect communication between the various system elements. System performance characteristics, measured in terms of speed, reliability, suitability to a variety of purposes, and adaptability to changing technology are ultimately dependent on the particular bus structure that is used and its associated protocols. This standard defines the IEEE Std 1000 Bus, which may be used to implement general purpose, high-performance 8-bit microcomputer systems. Such a system may be used in a stand-alone configuration, or in larger multiple-bus architectures, as a private (or secondary) bus or a high-speed I/O channel. This standard is applicable to those systems and system elements with the common commercial designation STE Bus. It is intended for those users who plan to evaluate, implement, or design various system elements that are compatible with the IEEE 1000 Std Bus system structure. The physical attributes and method of interconnect utilized by boards and modules conforming to this standard are derived from several International Electrotechnical Commission (IEC) standards. These standards, when implemented jointly in a systems environment, result in a mechanical configuration commonly referred to as Eurocard. Appendix B lists such applicable standards which, where referenced, are considered as if incorporated with this standard. In particular the connector used by IEEE Std 1000 Bus boards is a 64-pin male connector utilizing the outside two rows (designated a and c rows), specified in IEC Publication 603-2,1 and the mating female connector is used on IEEE Std 1000 Bus backplanes. The recommended size for IEEE Std 1000 Bus boards is 100 mm ´ 160 mm (3.937 in 6.299 in), commonly referred to as a single height standard depth Eurocard. The IEEE Std 1000 Bus structure is based on the master-slave concept in which a master, having gained control of the bus, may address and command slaves. Masters and slaves communicate with each other by use of an asynchronous interlocked handshake protocol. This technique allows for the construction of computer systems that incorporate devices of widely varying speeds. Multiple masters may be implemented within a single system.