Bega's Battle - Sync Generator Replacement - Testing with Super Don NTSC decoder

 

I don't have a Data East chroma PCB so I decided to try rigging up a Super Don NTSC decoder.  The colors are a little off, but it works well enough for testing!

Bega's Battle Sync Generator Replacement - How to install

My Bega's Battle / Cobra Command / Road Blaster mod to allow Dexter and other Sony laserdisc players to work with these laserdisc games is almost complete!  Here is the video I've created that shows how to perform the mod.

Cobra Command (dedicated) confirmed working with Dexter!

 Very exciting progress to show here.

Thanks to Mike Treu for testing for me!

By the way, not only will this mod work with Dexter, but it will also work with the Sony LDP-1450 which Mike also tested.

The mod replaces 16K on the bottom Data East board with a custom PCB that I designed.  So unfortunately, it will require modifying the game hardware, which I have tried to avoid as much as possible but which was ultimately the only feasible solution I could find for these games (Bega's Battle, Cobra Command and Road Blaster).

After the mod is installed, the game will work with:

• The original Sony LDP-1000A (yes, I maintained backward compatibility)
• Dexter
• Sony LDP-1450 and probably most other Sony players.

Making a MC44144 tester for Cobra Command / Dexter research

I've pondered about whether the "obsolete" MC44144 chip could be useful for making Bega's Battle (and Cobra Command dedicated) work with Dexter.  Although it isn't in production anymore, from what I can tell, it's still fairly obtainable.

Here's the PCB I've designed to help test it and see how well it works.

Cobra Command wouldn't boot

I've been trying to get my Cobra Command boardset (Bega's Battle conversion) up and running.  I have no official wiring harness, so I've been making my own wiring + PCB adapters, including power, serial, and RGB video.  When I tried powering up Cobra Command and plugging it into Dexter I got nothing.

So I did what anyone who loves tedious troubleshooting work would do.  I sniffed the 6502 CPU to see where the program was getting stuck.

I found that the program was looping endlessly at a subroutine at 0xE176:

But I wanted to know what was calling this subroutine.  Through some clever triggering, I was able to narrow it down to this area of code:

So basically, the game is sending the "clear all" command to the laserdisc player and blocking indefinitely until it gets a response (which may never happen).

Conclusion?  Serial I/O isn't making it from the game to Dexter.

After some more poking around, the answer ended up being quite simple.

The game is communicating at 1200 bps!  I've never seen a game communicate this slowly to the laserdisc player!

I was getting tripped up because I was assuming 9600 bps and even after staring at the logic analyzer capture and seeing traffic, my brain just didn't make the connection that maybe everything on the game PCB was working correctly and I just was assuming the incorrect clock rate!

Cobra Command (MACH 3 hardware) successfully tested on Dexter

Matteo Marioni tested out Dexter and Cobra Command (MACH 3 hardware) and it seems to work perfectly.  This is great news.