DL11-W Serial Line Unit/Real-time Clock Option Operator's Manual

This document is an operator's manual for the DL11-W Serial Line Unit/Real-Time Clock Option (M7856), designed for PDP-11 computers.

The DL11-W provides two primary functions:

1. Serial Line Unit (SLU): It acts as a character-buffered communications interface. It converts serial data from external devices (like Teletypes and EIA terminals) into parallel data for the PDP-11 Unibus (receiver function) and converts parallel data from the Unibus into serial data for external transmission (transmitter function). The receiver and transmitter operate independently, allowing simultaneous two-way communication. It offers significant flexibility, with configurable parameters such as baud rates (independent for transmit and receive), character size, stop bit length, and parity selection, all set via on-board switches. It can also operate in active (source of 20 mA current) or passive modes and includes a maintenance mode for self-testing.
2. Real-Time Clock (RTC): It provides a line frequency clock that generates timed interrupts, allowing programs to measure the passage of time based on the AC power line frequency.

The DL11-W is packaged on a single quad integrated circuit module (M7856) that plugs into peripheral controller slots. Its operation is controlled through five device registers accessible by software, and it generates vectored interrupts for its receiver, transmitter, and line clock functions, with the line clock having the highest interrupt priority. Configuration is primarily done through dip-mounted switches on the module, which determine addressing, baud rates, data format, and operational modes.

The manual aims to provide information for understanding normal system operation, configuration, installation, and basic programming, rather than detailed troubleshooting.