Jeri Reverse Engineers an HC55564 Chip from an Old Pinball Machine

Jeri Reverse Engineers an HC55564 Chip from an Old Pinball Machine
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In her latest Intersil “Academy of Analog Pinball Wizardry” video, Jeri Ellsworth replaces an HC55564 Continuous Variable Slope Delta (CVSD) codec chip with one she reversed engineered into an FPGA. What in blue-blazes is a CVSD modulator? Watch the vid and find out — as usual, Jeri does a great job of showing how it works, how she reversed engineered it, and what the results are. As some have pointed out, you can still scare these chips up online, but this was more about proving and showing than just about fixing.

Continuous Variable Slope Delta Modulator – HC55564

8 thoughts on “Jeri Reverse Engineers an HC55564 Chip from an Old Pinball Machine

  1. John Mangan says:

    Wow, amazing job Jeri! (as always). I would love to see more of the actual process that you use to get this information.

    1. Anonymous says:

      Good point, John. I had the same thought, watching the vid. I understand enough to know, conceptually, how this sort of thing works, but I have no idea how you actually go about getting the information on how the chip functions out of the chip itself(?). I assume all of this was not from data sheets and info found online. I’ll try and get Jeri over here to give us some clues.

  2. Anonymous says:

    Grammar police: “… and what the result is” (not are).  Or “results are”, take your pick.

    Otherwise excellent!

    1. Anonymous says:

      Oops. Yes. Typo. Missed the “s.” Fixed.

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Gareth Branwyn is a freelance writer and the former Editorial Director of Maker Media. He is the author or editor of over a dozen books on technology, DIY, and geek culture. He is currently a contributor to Boing Boing, Wink Books, and Wink Fun. His free weekly-ish maker tips newsletter can be found at

View more articles by Gareth Branwyn


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