VAX-11/780 RH780 Massbus Adapter Technical Description

This document provides a technical description of the RH780 Massbus Adapter (MBA), a crucial interface designed by Digital Equipment Corporation.

The RH780 MBA acts as the bridge between the Synchronous Backplane Interconnect (SBI), which connects to the VAX-11/780 processor and memory, and Massbus storage devices like disks and tapes.

Key aspects of the document include:

• Interfacing: It details how the MBA communicates with both the high-speed, 32-bit SBI and the 16-bit Massbus, managing data transfer, command execution, and status reporting.
• Architecture: It describes the internal structure of the MBA, including its control path, data path (which includes a silo for data buffering), and various internal registers.
• Operation: The document explains how the MBA handles different types of operations, such as writing to and reading from internal and external registers, and performing Massbus data transfers.
• Virtual Address Translation: It covers the MBA's role in translating virtual addresses from the SBI into physical addresses for Massbus devices.
• Error Handling and Diagnostics: Significant attention is given to the MBA's robust error detection capabilities, including parity checking, timeout mechanisms, and various fault conditions, as well as its diagnostic features.
• Programming and Specifications: It outlines the programming definitions, specifications, and register assignments (Configuration/Status, Control, Status, Virtual Address, Byte Count, Diagnostic, MAP, and Command/Address Registers) necessary for interacting with the MBA.

In essence, the RH780 Massbus Adapter is a sophisticated hardware component that enables efficient and reliable high-speed data transfer between the VAX-11/780 central system and its Massbus-compatible storage peripherals.