
The mystery of the Zombie RAM (2014) - isp
http://wp.josh.com/2014/03/03/the-mystery-of-the-zombie-ram/
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isp
"LED as power generator" on Electrical Engineering Stack Exchange:
[https://electronics.stackexchange.com/q/217765](https://electronics.stackexchange.com/q/217765)

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mchahn
I was developing a test rig for a cmos rom back in the 70's (yes, HP made cmos
roms). I was testing my test rig and as usual I tested removing the power pin.
The test kept passing so I thought my rig was screwed up. It turns out that
the input signals were powering up the chip through the same protection diodes
mentioned in the article.

Edit: One would think that if the input test vector included an all-zeros case
the chip would fail. It turns out this didn't happen because there were two
chip-enables, one true and one false.

