How do I setup the TRS-80 Model 100 to use an external 80col. 30 row dumb terminal so I can control the TRS-80 Model 100 ... BASIC from the dumb terminal?

I have a VersaTerm connected to a VGA monitor and USB Keyboard. I have a serial cable from the TRS-80 Model 100 to the VersaTerm serial port.

The VersaTerm is setup for 9600 BAUD 8N1 ...

  • 5
    I never heard of doing that, but no expert on it. What I have heard of is using the Model 100 as a terminal into something else. Sep 2, 2022 at 11:35

1 Answer 1


How do I setup the TRS-80 Model 100 to use an [...] dumb terminal so I can control the TRS-80 Model 100 [...]?

You won't get around programming this.

On board software like the TELCOM program, as well as all other software I know, is meant for the other way around - using the M100 as terminal on another computer.

That program must somehow replace the keyboard read and LCD output routines with it's own and handle the serial interface accordingly. Except, this might be difficult as the M100 is a ROM based system, so each and every routine is fixed in ROM. Then again, I think I remember a video interface for the M100, so there might be a way to redirect at least the output.

BASIC/ROM routines offer two ways of indirection. There is

  • a generic function dispatcher using RST 7 plus a function byte and
  • BASIC itself moves a lot of vectors into RAM, which may include a posibility of I/O redirection.

I don't have either list at hand. A good start to look for more information might be Christopher Morgan's -"Hidden Powers of the TRS-80 Model 100", the standard reading to get an introduction to the low level workings of the M100.

Now, if it's just about a more comfortable editor (*1), there's still the option to write your basic program on a PC and download it to the M100 (*2) using TELCOM to capture it in a file and open that file in BASIC. Heck, it might even work directly

  • Start BASIC
  • Type LOAD:COM:98n1e to initialze the serial with 19200 and 8N1, and wait to load the program
  • let the PC send the program (*2)
  • When done press CTRL-Z on the M100

Now the program should be in BASIC-memory. Just list and start :)

The other way around should work similar (using SAVE:COM:98n1e)

Last but not least, there is a software called desklink that lets a PC act as disk drive to the M100. Best place to start a search might be the CLUB 100 website - a must for M100 users anyway.

*1 - I think the one supplied is rather magnificent for an 8 bit handheld.

*2 - A simply `type x.bas>COM1:' will do it

  • 1
    Hi, Thanks. Damn, that sucks! I really wanted to use the VersaTerm for a larger more friendly display to the Model 100. OTOH, maybe somebody can write a small assembly language program to perform the trick?
    – wperko
    Sep 2, 2022 at 15:39
  • 3
    @wperko the main purpose of an M100 was to type notes in the field, then use a modem to upload them to a central computer. News reporters loved them.
    – RonJohn
    Sep 2, 2022 at 17:35
  • 1
    @wperko - if it had been easy or useful, someone would've created that remote access tool already. The Model 100 has had all sorts of ingenious hacks done with it, but it is at heart a very tiny 80c85 system. May try developing on an emulator, and upload the code to your real Model 100 once it works?
    – scruss
    Sep 4, 2022 at 16:49
  • Hi, That would be cool to try. I'd need full instructions how to import the program and run it though.
    – wperko
    Sep 5, 2022 at 17:10

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