No VTL-2

[Tom Lake]

When I follow the instructions on page 22 of the manual by setting A0 up while holding RESET DOWN and powering up, I 680 monitor message. If I do a J FC00 the simulation bombs out. I know switch A0 is good. In HLT mode, I can turn the A0 LED on and off by flipping the switch.

Is there a problem with VTL-2 or do I have another fault in my system?

[Chris Davis]

Are you connecting via USB?  If so, are you holding down RESET when you connect with your terminal emulator software?  The Arduino Due resets when connecting.

What text is displayed first when you connect?

[Tom Lake]

Yes, I connect via USB on the Programming port at 115200 baud. I hadn't tried holding down the RESET while starting TeraTerm. 

I just tried it, though, and all I get are two dot prompts and then a lock-up. No keys have any effect.

[Tom Lake]

I just tried it both ways: TeraTerm running before bootup and after bootup. Neither way works. After I booted up, I examined FC00 and a few bytes more. They're all FF.

There's nothing being loaded into memory.

On Saturday, January 24, 2026 at 8:50:08 AM UTC-5 famousd...@gmail.com wrote:

[Chris Davis]

You need to tell me what the banner says when you connect.  If it's locking up after showing two prompts, you have other problems beyond the VTL-2 ROM not loading.  I know you've replaced the Arduino.  Did you load the software from 12/7/2025?

[Tom Lake]

Software dated 12/7/2025. 

Here are the two sequences

1. TeraTerm running. 680 off. Hold down RESET while plugging in USB cable to Programming port. Release RESET.
Result: 
Starting Altair 680 Emulator: Monitor ROM loaded.
.J FC00
Simulation halted!
Last instruction executed: PC=D812 opcode=3E
PC=D813 SP=38F9 IX=00F6
A=FF B=6A CCR=D9

2. TeraTerm not running. 680 on. Hold down RESET while starting Teraterm. Release RESET.
Result:
.
. <blinking cursor after second prompt>
No keys work.

[Chris Davis]

The banner says what ROM is loaded.  If it doesn't say "VTL-2 ROM Loaded" then J FC00 will cause the simulator to crash.
You didn't mention what address switches were up.

When you say "680 on", do you mean it is connected to a power source?  Don't do that if you're connecting via USB.

[Tom Lake]

I figured the banner was wrong but that's exactly what I see. I have A7 (115200 baud) up and A0 (VTL-2 Monitor) up, the others down.

I was connected to USB. I'll not do that in future experiments.

[Tom Lake]

I got it to work! I plug in the USB connector to power the 680. Then I set the address switches. Next I start TeraTerm while holding down the RESET switch.

Voila! I get the VTL-2 ROM loaded prompt. I had been using the New Connection menu choice in TeraTerm. That won't work.

On Saturday, January 24, 2026 at 6:01:55 PM UTC-5 famousd...@gmail.com wrote: