VT1XX-AC

This document serves as a user guide for the VT1XX-AC serial printer interface option, designed for use with Digital Equipment Corporation's VT100 and VT132 video terminals. The VT1XX-AC provides an Electronic Industry Standard (EIA) RS-232-C compatible interface, allowing these terminals to connect to a local serial printer.

The guide covers the option's purpose, installation requirements (including necessary hardware like the Advanced Video Option and null modem cables, which are not included in the kit), and general hardware and software considerations. Installation is field-installable, ideally by a Digital Field Service representative due to the need for configuring PC boards, installing ROM ICs, and potentially soldering jumpers.

Key operational aspects include controlling print operations from both the terminal keyboard (using the PRINT/ENTER and SET-UP keys) and a host computer (via ANSI and VT52 mode command sequences). Four main print operations are detailed: Auto Print (line-at-a-time), Print Screen, Print Cursor Line, and Printer Controller. The document emphasizes the importance of a "Printer Ready Check" before printing, where the terminal suspends operations if the printer is not online or ready, indicated by a flashing VT1XX-AC indicator.

The SET-UP mode is extensively described, showing how the VT1XX-AC option alters the terminal's configuration settings. New SET-UP B and C features are introduced for configuring the serial printer interface, including receive/transmit speeds (baud rates), data bits per character, parity selection, print extent (full screen or scrolling region), and print termination characters. Proper matching of these settings with the serial printer is crucial.

Programming details explain how the host computer uses specific ANSI and VT52 escape sequences to control print operations and report terminal parameters. It also covers methods for preventing input character buffer overflows using XON/XOFF (DC1/DC3) control characters, outlining the terminal's 128-character buffer and associated warnings. Character set selections for printing are also discussed.

The communication interface is detailed, including the 25-pin DB connector pin assignments and signal interpretations, highlighting the DTR signal's priority for printer status. Finally, the guide provides procedures for option checkout, including power-up self-tests and communication/printer interface data loopback tests, along with explanations of error codes used to indicate hardware failures.