Dolphin Massbus Adapter Functional Spec Oct78

This preliminary functional specification, dated October 30, 1978, describes the Dolphin Massbus Adapter (MBA), also referred to as the RH30. Its primary purpose is to interface the Dolphin Bus with the DEC Standard Massbus, ensuring functional compatibility with TOPS10, TOPS20, and VAX/VMS operating systems.

Key aspects of the specification include:

• Functionality: The MBA supports up to eight Massbus devices (disks, tapes), with one device active at a time for data transfer. It provides access to internal and external registers, manages primary and secondary device commands, and includes an 8-word data buffer to average transfer rates. It also implements "read reverse" for tape handling.
• Performance Goals: The adapter aims for Massbus transfer rates of 2 M words/second (18/16 bit) and Dolphin Bus rates of 1 M word/second (36/32 bit), with a commitment to support future disk products up to 3.0 M bytes/second.
• Diagnostic Features: The design prioritizes clear distinction between controller and device failures, offering loopback capabilities, program simulation of control signals, and board-level fault isolation. However, chip-level fault isolation and self-diagnosis are explicitly not included as goals.
• Physical Design & Cost: The MBA is planned for implementation on three extended HEX multilayer modules, with an estimated cost of $2000 and a total power dissipation of 212.44 watts.
• System Interfaces: It details the 63 signals of the Dolphin Bus and 56 signals of the Massbus (divided into control and data buses), along with their definitions. Specific protocol and timing details for both buses are marked "To be supplied," indicating incompleteness.
• Channel Operation: The document describes distinct channel operations for TEN systems (using RH20 and MBOX components, Command List Pointers, and Channel Command Words, including a "SKIP" function) and VAX systems (utilizing RH780, Virtual Address, Map, and Byte Count Registers with a focus on byte handling). A proposed Dolphin MBA channel aims to merge VAX's byte handling with TEN's command format and backup register facilities.
• Programming Interface: It outlines numerous Massbus Adapter Registers (MARA) for configuration, control, status, diagnostics, block addressing, transfer control, and channel command words, detailing their purpose and access methods.

The document is noted as preliminary throughout, with several sections, particularly those related to protocol and timing, still awaiting full definition.