Overview
ISO/IEC 11458:1993 - Information technology: Microprocessor systems - VICbus - Inter-crate cable bus defines a standardized inter-crate (inter-chassis) cable bus for connecting multiple microprocessor-based devices. The standard specifies the electrical characteristics, signal assignments, bus protocols, timing rules and mechanisms required to build robust, fault-tolerant multi-device systems. It also provides terminology, register definitions and guidance for interfacing with backplane bus systems such as VMEbus (IEC 821).
Keywords: ISO/IEC 11458:1993, VICbus, inter-crate cable bus, VMEbus, microprocessor systems, cable bus, fault-tolerant.
Key Topics
- Scope & objectives: standardizes a cable bus for interconnection of devices and backplane systems; promotes interoperability and fault tolerance.
- Data transfer bus (DTB): defines DTB cycle types (direct and transparent), address/data lines (e.g., AD31–AD00), control lines (CL3–CL0), identification and device-number signals, block transfers, read-modify-write cycles, and detailed timing rules.
- Arbitration: protocols, arbiter/requester roles, arbitration lines and timing to control DTB mastership and avoid bus contention.
- Interrupts: interrupt lines, selection, protocol, interrupter and handler behavior, timing regulations.
- Utilities & fault tolerance: reset mechanisms (VICRESET), arbitration lock (ALOCK), device-failure signaling (DEVFAIL), online/offline states, cable connection/disconnection rules for robust systems.
- Electrical specifications: bus driver/receiver behavior, cable characteristics, connectors, terminators and termination power; continuity rules for offline devices.
- Registers & identification: control and status registers (CSR), online register (OLR), device operational register (DOR), reset register (RR), transparent and device identification registers (TR, DIR).
- VMEbus interfacing: annex material on mapping VICbus cycles and signals to VMEbus semantics (transparent cycles, AM codes, RETRY* behavior).
Applications
- Designing inter-chassis communications for embedded and industrial microprocessor systems.
- Implementing cable-based extensions of VMEbus systems or integrating stand-alone apparatus with backplane buses.
- Building fault-tolerant server clusters, modular instrumentation, or real-time control systems that require deterministic bus arbitration, interrupts and robust cable handling.
- Specifying cable/connector and termination schemes for multi-device installations.
Who uses this standard
- System architects and hardware engineers designing modular microprocessor systems.
- Embedded systems integrators working with VMEbus or similar backplane technologies.
- Test & validation engineers implementing timing, arbitration and interrupt behavior.
- Product teams producing device interface hardware (cables, terminators, bus transceivers).
Related standards
- IEC 821 / VMEbus specifications (for backplane compatibility and interface mapping).
- Relevant electrical and connector standards referenced for cable and termination practices.
This standard is essential when you need a documented, interoperable approach to inter-crate communication, deterministic bus protocols and reliable fault-tolerant behavior in microprocessor systems.