DZQ11 Asynchronous Multiplexer User's Guide

This document is the User's Guide for the DZQ11 Asynchronous Multiplexer, model EK-DZQ11-UG-001, published by Digital Equipment Corporation in August 1984.

The DZQ11 is a Q-bus option designed as an asynchronous multiplexer that interfaces a Q-bus processor with four asynchronous serial data communication lines. Its primary applications include data concentration, real-time processing, and cluster control. It is compatible with RS-232-C (V.28) and RS-423-A (V.10/X.26) standards and offers sufficient modem control for full-duplex dial-up and point-to-point/multipoint operations.

Key programmable parameters for each line include baud rate (16 selectable rates, up to 19,800 non-standard), character length (5-8 bits), number of stop bits, and parity (odd, even, or none). Additional features are limited modem control, zero receiver baud rate, break generation and detection, silo buffering for received data, and line turnaround. It is program-compatible with Q-bus DZV11 and UNIBUS DZ11-A (excluding 20 mA operation and line count).

Physically, the DZQ11 consists of two main components:

1. The M3106 module (a dual-height module with all active circuitry and I/O connections).
2. A distribution panel (containing four D-type connectors) that connects to the M3106 via a ribbon cable. Various cabinet kits are available for installation into different systems, offering different cable lengths and, in some cases, noise filtering and static discharge protection.

Installation procedures cover unpacking, inspection, setting modem control jumpers, and configuring device address and interrupt vector assignments via switches (E28 for address, E13 for vector). Special attention is given to anti-static measures and power precautions. Diagnostic tests (e.g., CVDZA, CVDZB, CVDZC) and test connectors (H329, H325) are provided for verifying proper operation. The guide also details rules for assigning floating addresses and interrupt vectors within a Q-bus system.

The document describes six addressable device registers used for controlling and monitoring the DZQ11:

• Control and Status Register (CSR): Manages overall operations, including master clear, scan enable, and interrupt enables.
• Receiver Buffer (RBUF): A read-only register holding received characters, line number, and error flags (parity, framing, overrun, data valid).
• Line Parameter Register (LPR): A write-only register to set per-line communication parameters like character length, stop code, parity, and speed.
• Transmitter Control Register (TCR): Enables transmission on specific lines and controls Data Terminal Ready (DTR) signals.
• Modem Status Register (MSR): A read-only register showing the status of modem signals (Ring Indicator, Carrier).
• Transmit Data Register (TDR): A write-only register for loading characters to be transmitted and controlling break signals.

Programming aspects focus on efficient control. It details how to manage interrupts (Receiver-Done, Silo-Alarm, Transmit) by setting appropriate CSR bits, allowing for polling-based, per-character, or silo-alarm-driven (after 16 characters) reception. It explains the process of emptying the silo (reading RBUF until data valid clears) and transmitting characters (setting line parameters, enabling transmission, and loading the TDR). The guide also covers Data Set Control through the DTR bits in TCR and sensing Carrier/Ring status from the MSR.