Atari 2600 pause mod - exxos style

[exxos]

Forgot all about this project :lol:

I reviewed some of the popular pause mods and they all basically sucked. Some of the designs for them made no sense whatsoever. But the thing is you can only pause the CPU on a read cycle I think (I forget which) none of the other mods did that. So it would intermittently crash the thing :roll:

So I wrote some GAL code to correctly synchronise to the CPU and pause at the proper place to avoid the crashes and add a pause by joystick feature as well. Like with all things Atari, the load of the GAL on the joystick port caused the joystick to malfunction so we ended up having pullups on it :lol: :roll:

So basically this one with a extra button on the joystick you can trigger the pause by pressing up and down at the same time. Generally no games are going to do that because it is physically impossible. So that is used to pause and unpause the game.

This in itself created a problem because of switch bounce on the joystick itself :roll: It was almost impossible to simply press it once. The GAL could trigger even on the slightest bounce and it could oscillate several times. Which was rather annoying. Various attempts to solve this basically failed. So I ended up using the reset chip that we used on the H5 as a one second delay. So it becomes a one-shot sampling circuit where it will only sample and register one change every second. This thankfully solved that problem.

But I didn't stop there :lol: Some people who did did not like the corruption left on the screen while it was paused and indeed you could get audio noises because the CPU was basically hung. So this is the reason for all the bodge wires. They basically zero all the colour and audio signals while it is in pause mode so you do not get the screen corruption or audio sounds. And of course when you unpause, the video and audio is yet again enabled. The only slight "problem" is that like on my TV, would go into standby without a video signal input :roll:

IMG_5781.JPG

IMG_5802.JPG

This video shows the screen corruption on pause. Also it shows switch bounce problem.





This was a later build which solves the above issues.