DHQ11 User Guide

This document is the DHQ11 User Guide, providing comprehensive reference information for the DHQ11 asynchronous multiplexer.

Core Functionality: The DHQ11 is an eight-channel, full-duplex serial-line interface designed for Q-bus systems. Its primary application is interactive terminal handling, data concentration, and real-time processing.

Key Features:

• Dual Programming Modes: Operates in either DHV11 or DHU11 mode (DHU11 is the preferred and generally more performant mode, reducing CPU overhead).

• Data Transfer:

  • Transmission: Supports Direct Memory Access (DMA) transfers or programmed transfers (1-character buffer in DHV11, 64-character FIFO in DHU11).
  • Reception: Features a large 256-entry First-In, First-Out (FIFO) buffer for received characters, dataset status changes, and diagnostic information.

• Communication Standards: Supports either EIA-232-D/V.28 or DEC423 (a data-leads-only implementation of RS-423-A using MMJ connectors) via different cabinet kits. DEC423 is recommended for longer distances (typically 1000 ft at 9600 baud).

• Performance: Achieves a total module throughput of up to 60,000 characters per second (8-bit characters, all channels at 38.4 kbaud). Each channel can be individually programmed for 16 speeds from 50 to 38,400 bits/s.
• Modem Control: Provides full modem control signals for auto-answer dial-up operations.
• Flow Control: Supports automatic XON/XOFF operation to prevent data loss, with configurable filtering of XON/XOFF characters.
• Diagnostics: Includes built-in self-test sequencers with LED status indication and a Background Monitor Program (BMP). It is compatible with MicroPDP-11 and MicroVAX II diagnostic systems.
• Bus Compatibility: Supports 16-, 18-, or 22-bit Q-bus addressing, including block-mode data transfer.

Physical and Installation:

• Module Type: A single dual-height Q-bus module (M3107).
• Configuration: On-board switchpacks (E-19 and E-11) are used to set the device's Q-bus base address, interrupt vector address, and the programming mode (DHV11 or DHU11).
• Connections: Connects directly to the Q-bus and interfaces to communication lines via distribution panels and specific cables (BC05L-xx for module to panel, and various null modem/full modem cables).

Programming and Operation:

• Registers: Controlled and monitored via Q-bus-addressable registers, including Control and Status Register (CSR), Receive Buffer (RBUF), Transmit Character Register (TXCHAR), Line-Parameter Register (LPR), Line-Status Register (STAT), and DMA control registers.
• Initialization: The module performs a self-test and sets default channel characteristics upon bus reset or master reset.
• Configuration: Line characteristics (speed, data bits, parity, stop bits, flow control, mode) are configured via LPR and LNCTRL registers.
• Interrupts: Generates receive and transmit interrupts, with distinct vector addresses.

Troubleshooting: The guide outlines procedures for isolating communication problems, involving checking the module, terminal, cabling, and using internal and external diagnostic programs (self-test, BMP, MicroPDP-11, MicroVAX II diagnostics). It also lists Field-Replaceable Units (FRUs).

In essence, the DHQ11 User Guide is a comprehensive manual for installing, configuring, programming, and troubleshooting the DHQ11, an 8-channel asynchronous serial multiplexer for DIGITAL's Q-bus systems.