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Atari 2600 ABS Device


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The ABS device (ABsolute non-Sense device) is an interface for Atari VCS system that allow to capture a defined game parameters, such as remaining lives, score and so on.

It's interfaced with cartridge, where the address-bus lines are routed to a PLD and data-bus lines are routed to external devices (i.e. microcontroller or latch chip...)

PLD is programmed in order to respond to a defined address value: when the address value programmed match the address value present on the bus of VCS, a PLD's output pin is set, so the external devices know that the preset address in on the way and they read the related data present on data-bus.

For example, in Pole Position game, at RAM address 88 (hex) is stored the car's speed; programming the PLD with preset address equal to 88 (hex), we can read the data associated to the car's speed (i.e. with a microcontroller interfaced with Atari data-bus and with the active output of PLD).



In this case the car's speed is grabbed form Atari VCS memory ram , and it is displayed as led bar. The led bar value is equal to the speed-bar already present on the game.



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:cool: Interesting project. How are you going to add a user interface on to it so that it becomes something like the game genie?

This is only a project for fun, no user interface will be develop. I like to explore such kind of expansion device for a future game project, in order to add, for example, external 7-segment lcd and/or leds, may be for a porting game like sega monaco gp...

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  • 5 months later...

Im very interested in any hardware made for the 2600. this is pretty cool!


If you could make this into a pass though cart. like you stick it in the atari and stick the game into it. and it has like 3 leds and it just displays whatever info it can grab, lives remaining, speed, ect. even if it just blinks when you shoot or the leds move with the sound.


very cool man. ide love to talk to you more about hardware!

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  • 3 weeks later...

You'd need a way to decode addresses and store the data bus values somewhere, until they are updated. A 74HC688 is an 8 bit address decoder. Take 2 of those tie them to a 74LS08 AND gate. Put a buffer on the data lines like the 74LS244, with the '244 updating every time the AND gate goes high and you're set. Now comes the fun part, displaying that stuff. You could construct a simple resistor ladder DAC and feed its output to a LM3914 bar graph driver or a Volt meter.


Or you just take a microprocessor like this Arduino thingie or a PIC or similar stuff.

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