DZ11 Maintenance Manual

This document is the "DZ11 Maintenance Manual," a preliminary edition from January 1977, published by Digital Equipment Corporation.

The DZ11 is an asynchronous multiplexer designed to interface a PDP-11 processor with up to eight asynchronous serial lines. It supports a wide range of applications, including communications processing, time-sharing, and real-time processing, handling both local (EIA RS232C or 20mA current loop) and remote (modem-based, full-duplex) operations.

Key features of the DZ11 include flexible control over communication parameters such as baud rate (up to 9600 baud), character length (5-8 bits), stop bits, and parity. It provides receiver and transmitter interrupts, limited data set control, break generation/detection, and a 64-character silo for buffering received data. Physically, the DZ11 consists of a single hex SPC module (M7819 for EIA, M7814 for 20mA) and an unpowered distribution panel (H317-E or H317-F). A single distribution panel can support two DZ11 modules, offering up to 16 lines. Its internal architecture comprises a Unibus Interface, Control Logic (including a scanner and various registers), and Line Interface (utilizing Universal Asynchronous Receiver-Transmitter (UART) integrated circuits).

The manual is structured into five main chapters:

• General Description: Introduces the DZ11's function, physical characteristics, performance specifications, and high-level functional components.
• Installation: Provides detailed procedures for unpacking, inspecting, configuring, and physically installing the DZ11 modules and distribution panels.
• Programming: Explains the device's registers (Control and Status, Receiver Buffer, Line Parameter, Transmit Control, Modem Status, Transmit Data), programming features, and includes examples for various operations.
• Detailed Description: Delves into the theory of operation, describing data flow, the Unibus interface, the scanner's timing and control functions, and the specific roles of each register and the UARTs.
• Maintenance: Outlines preventive and corrective maintenance procedures, listing required test equipment and detailing the use of specialized software diagnostics (DZ11 Diagnostic, System Exerciser, and ITEP Overlay) to troubleshoot and verify the system's operation through various test modes (Internal Loopback, Staggered Loopback, External, On-Line with Terminal).

The document serves as a comprehensive guide for understanding, installing, programming, and maintaining the Digital Equipment Corporation DZ11 asynchronous multiplexer for PDP-11 systems.