DU11 Single Line Programmable Synchronous Interface User's Manual

This user's manual describes the DU11 single-line programmable synchronous interface designed for the PDP-11 family of computers.

The DU11 is a program-controlled, double-buffered communication interface that facilitates serial-to-parallel and parallel-to-serial data conversion, EIA-to-TTL voltage level conversion, and modem control for full or half-duplex communication systems. It supports both synchronous and isochronous communication modes, with configurable character length (5 to 8 bits, with optional parity) and sync character settings, all controlled through software.

The manual covers:

• Introduction: Explaining data communication techniques (asynchronous, synchronous, isochronous), a general description of the DU11's capabilities, its physical characteristics (M7822 Quad Integrated Circuit module, compatibility with Bell 201/303 modems), and performance specifications.
• Installation: Detailed instructions on mounting the DU11 module (DU11-DA and DU11-EA models) in various PDP-11 mounting panels, installing modem cable harnesses, and configuring Unibus and interrupt vector addresses using switches and jumpers.
• Device Registers and Interrupt Requests: A comprehensive breakdown of the five program-accessible device registers (Receiver Status, Receiver Data Buffer, Parameter Status, Transmitter Status, and Transmitter Data Buffer), including their address assignments and bit-level descriptions for control and status monitoring. It also explains how the DU11 generates interrupt requests for both receiver and transmitter operations.
• Programming Requirements and Recommendations: In-depth guidance for programming the transmitter and receiver in both synchronous and isochronous modes, covering steps such as loading parameters, enabling operations, transmitting/receiving sync characters to establish and maintain synchronization, and detecting message completion or errors.

The document assumes a reader familiar with basic digital computer theory and is intended for those involved in installing, configuring, and programming the DU11 interface.