Falcon Switchable Multisync Cable

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This adapter has one purpose only, and that is to adapt an ST compatible Multi-sync to the Falcon. It will not enhance the use of a VGA monitor, and may damage it with sync-rates it cannot use. However, if you have a Multi-sync, it will allow you to use all the 1224/TV modes on it as well as VGA modes.


I take NO responsibility for damage to anyone's Falcon, Monitor, or Sanity as a result of this information. I encourage you to verify my data and DO NOT attempt this unless you are familiar with soldering (especially cable-making). TURN OFF your monitor and Falcon prior to connecting this device, and TURN OFF your Falcon IMMEDIATELY if it does not work as expected, and recheck your work.

Okay, with that out of the way, let me describe what this thing does. The Falcon's new enhanced video port has 2 pins that inform the machine of the monitor connected. These are Monitor Select 1 and 0. These are the possibilities:

      M1  M0   Monitor type
      0   0    ST Monochrome
      0   1    ST Color
      1   0    VGA
      1   1    TV

Now, the Atari adapter that you connect to the Falcon pulls down these pins. If there is no adapter, the pins remain high signaling TV mode. The 2 modes we want to emulate on the Multi-sync are ST color and VGA (We can select ST Monochrome from the Set Video menu already).

First we need to construct a simple VGA adapter as follows:

     Falcon 030 pin (DB19)|VGA pin (HD15)
     Red                1 | 1
     Green              2 | 2 
     Blue               3 | 3
     Ground             5 | 5 *
     Red Ground         6 | 6
     Green Ground       7 | 7
     Blue Ground        8 | 8 
     Ground            10 |10 
     Ground            11 | 5 * 
     Hsync             13 |13
     Vsync             14 |14

Note that I used all the ground pins in the video port and I tied 2 of them (*) to the same VGA pin. All this grounding may not be necessary, but I wanted the cleanest signal possible.

Now, we need to make use of the monitor select lines to choose our mode. I used a SPDT switch and wired it this way:

      |_______|   Bry's amazing rendition of a toggle slide switch.
        | | |
        1 2 3 
     Falcon Pin|Switch Pin
     M1      18| 1 (throw)
     M0      19| 3 (throw)
     GND     11| 2 (pole)

This will alternately pull M0 and M1 low, resulting in a selection of ST Color and VGA mode.

I constructed my adapter using a 12 conductor wire with shield, but you may use as few as 9 if you tie the grounds together. I do not reccomend tying R,G and B grounds into the same wire. You may not need shielded wire if you use a short length (my adapter is about 6 inches long). I got a mini slide switch from Radio Shack and mounted it in the DB 19 hood. If you do this, you must be careful to route wires around the switch when assembling the hood, and the switch must be placed away from the DB19 connector, so it does not get in the way of the solder cups. Basically, plan out your construction, because those DB19 hoods are hard to come by (order 2 to allow for mistakes!).

    • Using the Adapter **

The Falcon TOS looks to M0 and M1 upon boot-up and everytime a program does a Setscreen (a change of video mode), so this switch can be flipped on the fly for programs that only run on a certain monitor. One example is the PLASMA30.PRG demo. If you are in VGA mode, it will not set the correct screen, and will look distorted, however, if you flip the switch before running it, the next Setscreen call made by the demo will choose a 1224 mode correctly. This gives you the most from your Multi-sync monitor: The ability to select any mode the Falcon can do.

Feel free to send comments, questions, and ESPECIALLY errors to:

   Bryan Edewaard 
   Email: bryedewaard@delphi.com


   DB9/HD15 hood, Toggle switch - Radio Shack
   DB19 female solder connector, HD15 female solder connector,
   DB19 Hood - Best Electronics
   Misc... 9+ conductor wire.