LA75 Companion Printer Programmer Reference Manual

This Programmer Reference Manual for the LA75 Companion Printer provides comprehensive technical information for software developers to effectively utilize all of the printer's features.

The document is organized into three main parts and several appendices:

1. General Information: This section introduces the LA75 as a compact dot matrix printer, highlighting its text and graphic printing modes, downline-loadable memory, and serial interface capabilities (up to 9600 baud, 2KB input buffer). It details printer communication, interface signals, data formats, baud rates, input buffer control (XON/XOFF protocol), and the functions of the front panel controls and self-tests.

2. LA75 in DEC-Compatible Mode: This extensive part describes how the printer processes characters and commands when operating in its native DEC-compatible mode (emulating LA50 or LA210). It covers:

   • Character Processing: Explains 7-bit and 8-bit environments, character set mapping, and the functions of various CO (7-bit) and C1 (8-bit) control characters (e.g., Bell, Backspace, Line Feed, Form Feed, Shift In/Out, XON/XOFF, Cancel, Escape).
   • Escape and Control Sequences for Text Mode: Provides detailed formats and usage of sequences to control text printing functions, including horizontal and vertical pitch, page length, margins, horizontal and vertical tab stops, character set selection (including user-preference and downline-loadable sets), print quality (Draft, Memo, Near Letter Quality, Letter Quality), and highlighting (bold, italics, underline, superscript/subscript). It also covers automatic sheet feeder control.
   • Status, Report, and Reset Sequences: Describes commands for product identification, device status requests and reports, and various printer reset functions.
   • Graphic Mode: Explains how to print graphic images using the sixel protocol, detailing picture data, sixel printable characters, and control codes specific to graphic printing.

3. LA75 in IBM Proprinter Emulation Mode: This section outlines the printer's functionality when emulating an IBM Proprinter. It covers:

   • IBM Emulation Features: Describes the line-oriented buffer, graphic mode overview, character size (standard, compressed, double-width), and escape sequence processing differences compared to DEC mode. It details the compatible character sets available (Set A, Set B, All Characters).
   • Escape Sequences for IBM Emulation: Provides the specific escape sequences for IBM compatibility, covering terminal management (reset, deselect printer), vertical and horizontal form handling (pitch, form length, margins, tabs), paper fault handling, unidirectional/bidirectional printing control, alternate character set mapping, and various printing modes (Draft, LQ, NLQ, Shadow Bold, Superscript/Subscript). It also details the downline-loading of character images to memory.

Appendices offer additional resources, including comprehensive character set charts, examples for DEC graphic mode images, BASIC programming examples for text mode functions, and alternative programming methods to optimize print quality and address potential limitations (e.g., multi-pass printing).