VT100

File:VT100 1.png

What is this all about?

When the Model 100 was released, it was offered with another product called the Disk Video Interface, which provided dual 5.25 floppy drives and ability to support an 80x25 CRT. It was well integrated with M100 OS, with several command s that extended BASIC's ability to control the CRT.

The Model 100 lends itself well to an attached terminal acting as a video adapter, and it turns out that a project provided by Geoff Graham of Perth Australia comes very close to fitting the need.

http://geoffg.net/terminal.html

This project (plus some minor extensions), combined with some disassembly and reconstruction work on Disk Basic, has yeilded a very nice external VGA video solution for Model 100!

Acknowledgements

I would like to acknowledge and thank those that have contributed to the project:

Ken Pettit - for VirtualT, and the core disassembly of Disk Basic

Philip Avery - for efforts with CP/M and attached Video using the VT100 Adapter

Geoff Graham - for the original VT100 Terminal Project

Supported Models

• TRS-80 Model 100, Tandy 102

The Hardware

There are several sources for the VT100 Adapter. I have developed a PCB version that is, I think, most convenient for Model T users as it has a native DE-9 connector for serial data connection.

Other sources are available. See http://geoffg.net/terminal.html and https://www.tindie.com/products/petrohi/geoffs-vt100-terminal-kit/

Note that these boards need a custom cable to connect with the M100.

The Software

The solution requires some software. Generally, you require 1. VT100 Driver software: stand alone equivalent of "Disk Basic" tailored for the VT100 Adapter 2. A patched version of the firmware for the VT100 Adapter, needed to enable certain M100 specific functions.

VT100 Driver

The following table has links to the current VT100 Driver software and source code.

Installation:

  NOTE: installation of the driver resets the DATE and TIME on your laptop.

  1. load VT100.CO into your Model 100.
  2. Enter BASIC, and issue command
  CLEAR 0, 60000
  3. Return to MENU, cursor over to VT100.CO and hit ENTER.

  The VT100 Driver code is now installed.  You can delete VT100.CO; the code is installed in uppper RAM.
  

I recommend downloading the Disk Video Interface User Guide to learn about how the DVI commands work. The VT-100 driver is essentially replicates the functionality, with a few differences:

  SCREEN command:
  Format of command is SCREEN X,Y
  X = 0, -> LCD
  X = 1, -> CRT attached to RS-232 port, 19200 8N1
  X = 2, -> CRT attached to "the BCR/Cassette port hack", Serial TTL at 57600 bps

  WIDTH command:  not functional. CRT is pinned at 80x24.

  Also, support for printing the CRT contents to Printer is not implemented.