VT100 firmware disassembly

This repository contains an annotated disassembly of the VT100 firmware ROM. VT100 is a video terminal introduced by DEC in 1978.

The disassembly can be assembled with an assembler such as asmx-8085 or vasm. That will generate a binary file identical to the original ROM. See Makefile for an example.

Status

• The annotation is incomplete.

• In OK shape:

  • Parsing of received UART characters

  • Processing of control characters, control sequences and escape sequences

  • Keyboard input processing

• Needs more attention:

  • UART RX/TX routines (SILO) and flow control

  • Video scrolling

  • SET-UP mode

  • Machine self-tests

• Pull requests are welcome.

• Have fun. :-)

Resources

These resources have been a great help when annotating the code:

• VT100 Series Video Terminal Technical Manual

  • Chapter 4 contains an in-depth description of the hardware and an overview of the firmware.

• VT100 schematics

  • Provides additional information on how the CPU is connected with the peripherals.

• Intel 8080/8085 assembly language programming manual

• Simulation of the VT52 and VT100 hardware

  • A nice tool for learning about the VT100 user interface when you don’t have access to the machine.

• Intel 8080 instruction disassembler