680 5-Bit Character Assembly Subroutines

This document describes a set of subroutines for the PDP-8 computer designed to handle Teletype communication. These subroutines manage the assembly and disassembly of serial-bit data into 5-bit characters, allowing the computer to communicate with up to 128 Teletype lines via the 680 Data Communication System.

Key features and requirements include:

• Functionality: The routines handle both input and output for multiple Teletype lines, managing start/stop bits and transmission in serial-bit format.
• Memory Usage: The program occupies approximately 400 octal locations, with additional space required for buffering based on the number of lines connected.
• Initialization and Usage: Users must call specific pseudo-commands (T5INIT, T5SOF, and T5SIR) to initialize the system, output characters, and test for incoming data.
• System Configuration: Requires a minimum PDP-8 configuration with 680 Data Communication System hardware. It also provides specific IOT instruction definitions for clock control.
• Technical Details: The document includes comprehensive information on storage requirements, interrupt service routines, flowcharts detailing the logic, and the complete source code listing for implementation.
• Performance: The document provides a timing table demonstrating the percentage of machine time consumed based on the number of lines and the baud rate (50 vs. 75 baud).