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Diodes are used between DATA3 and TL on the gun inputs to ensure that if DATA3 is low (which is used to identify a Justifier) it'll also pull down TL to keep the adaptor enabled. Light Phaser/Justifier to Justifier/GameGun adaptorĬompared to the previous circuit you'll notice the TL signal coming back from the console to the gun inputs has been removed along with the supporting diode logic near the mode switch. Now that I know it's possible to tap directly into DATA2 to get the unlatched light gun signal from the Justifier it removes the need to reset the gun every frame, which allows for somewhat simpler diagram: I think all of the additional routes for the signal to work its way through the circuit – as well as the crude diode logic used to avoid having to add even more logic chips – was causing timing issues. Unfortunately, with all these complications I found that Lethal Enforcers no longer worked reliably, for example pulling the trigger would advance two items in the menu instead of one.

The circuit had been adapted to tap into this unlatched signal on DATA2 when a Justifier as attached, but there was also some additional complications in the circuitry to ensure that when the adaptor was in "GameGun" mode it would still hold TL low to ensure that any connected Justifier was enabled as it couldn't rely on the game doing so. The American Laser Games don't reset the gun in this fashion, but they don't need to as they use DATA2 for the light sensor output from the gun instead of the latching TH. The latching behaviour of the light sensor output TH on the Justifier had caused one complication in the design of the adaptor, described in this earlier post in detail, and that is that there needed to be some way for the console to output the state of the TL back to the gun to reset TH each frame when TL goes high. Constructing a prototype of the updated Justifier adaptor for the Mega Drive