DV11 Communications Multiplexer User's Manual

This document is a User's Manual for the DV11 Communications Multiplexer, a hardware component designed for PDP-11 computers by Digital Equipment Corporation (DEC).

The manual provides operational and programming information for the DV11, which connects 8 or 16 serial data lines (modems) directly to PDP-11 core memory for bidirectional data transfer. Its primary function is to offload communication protocol processing from the PDP-11 CPU, handling tasks such as monitoring characters, managing data transmission/reception sequences, and computing error-checking codes (like LRC, CRC-16, and CRC-CCITT).

Key aspects covered include:

• Functionality: The DV11 comprises a Modem Control Unit and a Data Handling Section, working with an internal microprocessor and RAM. It uses Non-Processor Request (NPR) transfers for efficient data movement and processes characters based on a Core Memory Control Table set up by the PDP-11 program.
• Specifications: Supports synchronous (1200-9600 baud) and asynchronous (50-38400 baud) rates, 5-8 bit character lengths, various parity options, and full/half-duplex modes. It specifically implements Digital's DDCMP and IBM's BISYNC protocols, achieving a maximum throughput of 38,400 characters per second.
• Installation: Details site preparation (power, environment, Unibus placement), physical installation, and configuring the DV11's Unibus and interrupt vector addresses and synchronous parameters via DIP switches and jumpers.
• Programming: Explains how the PDP-11 controls the DV11 using directly-addressable and indirectly-addressable registers. It describes procedures for modem setup, data transfer initialization and termination, interrupt handling, and the implementation of BISYNC and DDCMP protocols through software.

In essence, the DV11 is a specialized communications interface that liberates the PDP-11 processor from the overhead of low-level communication tasks, enhancing system efficiency for multi-line data communication.