OpenVMS VAX Device Support Manual

This manual provides comprehensive information for system programmers to write and load device drivers for OpenVMS VAX Version 6.1. It covers the fundamental components and operating system environment of a device driver, including I/O processing, system synchronization mechanisms (like Interrupt Priority Levels and spinlocks), and hardware considerations specific to various VAX processing systems and I/O buses.

The document details how to code different parts of a driver, such as tables (prologue, dispatch, function decision), and routines (FDT, start-I/O, interrupt service, timeout handling, initialization, cancel-I/O, error logging, and cloned UCB). It also explains how to load and debug drivers using utilities like SYSGEN and XDELTA. Advanced topics include bus-specific details for UNIBUS, Q22-bus, MASSBUS, VAXBI, TURBOchannel, and VMEbus, as well as SCSI class driver support and the connect-to-interrupt facility for real-time applications. Templates and code examples are provided for common driver types.