DL11-W Serial Line Unit/Real-Time Clock Option Technical Manual

This technical manual (EK-DL11W-TM-002, 2nd Edition, October 1982) from Digital Equipment Corporation describes the DL11-W Serial Line Unit/Real-Time Clock Option (M7856), a hardware component designed for PDP-11 computers.

The DL11-W serves two primary functions:

1. Serial Line Unit (SLU): It acts as a character-buffered communications interface, converting serial data from external devices (like Teletypes or EIA terminals) to parallel data for the PDP-11 Unibus, and vice-versa. It supports simultaneous two-way communication.
2. Real-Time Clock (RTC)/Line Time Clock (LTC): It provides timed interrupts based on the AC line frequency, enabling programs to measure time.

The document provides comprehensive information for users with a basic understanding of digital circuitry and PDP-11 systems. Key aspects covered include:

• General Description: Overview of its capabilities and how it functions as a Teletype or EIA terminal control, including a maintenance mode for self-testing.
• Configuration & Installation: Details on setting various switch-selectable options such as baud rates (110 to 9600, with independent transmit/receive speeds), character size (5-8 bits), stop bit length, parity (odd, even, unused), current loop modes (active/passive), and address/interrupt vector selection. It also covers physical installation procedures and testing.
• Programming Information: Describes the five device registers (Receiver Status, Receiver Buffer, Transmitter Status, Transmitter Buffer, Line Clock Status), their bit assignments, interrupt mechanisms (with different priority levels for line clock, receiver, and transmitter), and timing considerations for various operations.
• Detailed Description: An in-depth explanation of the DL11-W's functional units, including address selection logic, register operations, interrupt request and control logic, the Universal Asynchronous Receiver/Transmitter (UART) for serial-to-parallel conversion, baud rate generation, maintenance mode, 20 mA current loop, and EIA level conversion.

The manual aims to help users understand system operation, analyze trouble symptoms, and determine corrective actions, but does not provide detailed troubleshooting techniques.