Evelands Dot Net

The Megaman PET is a cheesy little electronic toy that makes of use of collectable battle chips. In the games, these are memory cards with anti-virus programs in them. My son picked up a bunch of chips that were packaged with the action figures.

So we had to buy the PET...

Now it turns out, like most collectibles, the really cool chips are rare. They can be picked up for anywhere from a few bucks each to over fifty a piece.

Ouch.

The chips aren't much to look at. They appeared to be little more than a tiny PCB with some exposed traces that made contact inside the PET.

So how does the PET recognize the different chips? And, can I make a circuit that mimics each chip? I figured there were a couple of possibilities:

• A dumb circuit. A simple change in resistance across one or more traces or traces that were connected. This seemed likely considering the size of the chips and the relative cost of them (they basically package them as giveaways in other Megaman items...)
• Something more complex than the above. Maybe an IC or something in there...

After poking around with my continuity tester, it turns out they're pretty straight forward.

• One or more pins is always shorted (electrically connected) to the second right-most trace (counting left to right from one, Trace 10). Think of it as the 'ground' pin.
• Nothing ever seems to be connected to trace 11.
• The numbering looks vaguely like binary. For instance, chips number 018 (Spreader) and 019 (Heat Shot): 018 had pins 5,8 and 10 connected. 019 had 5,8,9 and 10 connected. Using binary to represent the contacts that can be connected (not 10 or 11), we get 000010010 and 000010011; eighteen and nineteen respectively. Sweet! Unfortunately, it doesn't always work out... Barrier is chip number 135. I expected it to be 010000111 ... instead pins 1,5,6,7 and 10 (100011100 or 284) were connected...

What's under the hood of the barrier chip...

Next >>