Storage System Diagnostics and Utility Protocol

This document outlines the Diagnostic/Utilities Protocol (DUP), which is used by Digital Equipment Corporation's mass storage controllers to load, start, and monitor diagnostic and utility programs. Complementing the Mass Storage Control Protocol (MSCP), DUP provides the communication method between a host class driver and a DUP server within the controller.

The manual covers:

• Communications Schemes: Explains how the host and controller interact using sequential message services and block data communication services, emphasizing the necessity of connection synchronization and flow control.
• Server States: Details the three major states of a DUP server (Offline, Available, Online) and sub-states (Idle, Active) relative to the host.
• Command Protocols: Defines the generic control message format and specific commands, including ABORT PROGRAM, GET DUST STATUS, EXECUTE SUPPLIED PROGRAM, EXECUTE LOCAL PROGRAM, and the SEND/RECEIVE DATA commands.
• Data Dialogue: Describes an optional sub-protocol for embedding standard terminal dialogues within SEND/RECEIVE DATA messages to allow transparent remote program execution.
• Appendices: Provides reference material on modifier/status codes, the structure of remote program headers, and the use of the "DIRECT" program for listing local directory information.