VAXstation 2000 and MicroVAX 2000

This document is a technical manual addendum for the VAXstation 2000 and MicroVAX 2000 systems, specifically detailing the DHT32 Asynchronous Serial Line Option.

The DHT32 option adds eight asynchronous serial lines to the system, implemented with a DHU-style interface. Key features and characteristics include:

1. Components: It consists of a controller module and a driver/receiver module, connected by a ribbon cable. The host system supplies power to the entire option. The driver/receiver module converts internal TTL levels to external DEC423 levels and provides electrostatic discharge (ESD) and electrical overstress (EOS) protection.
2. Functionality:
   • Provides eight data-lead-only serial lines (no modem control).
   • Supports independent baud rates up to 38400 bits per second.
   • Features a 256-character input FIFO buffer with a programmable hold-off timer and a 64-character per line output FIFO buffer.
   • Lacks output Direct Memory Access (DMA) support and modem control, differentiating it from other DHU-like products.
3. Operation: The module's functions are controlled through various word-addressable registers (e.g., Control and Status, Receive Buffer, Line Parameter, Transmit FIFO Data, Line Status, Line Control, Transmit Enable registers). A specific line must be selected via the Control and Status Register before accessing line-specific parameters or data.
4. Diagnostics: It includes internal self-tests that run on power-up and reset, and a continuous background test to detect and report errors. The document also details the module's default state after a successful reset.
5. Specifications: It outlines the electrical power requirements (+5V, +12V, -12V) and environmental specifications (temperature, humidity, altitude) for storage, operating, and nonoperating conditions.