I decided to finally let this little piece of information go out to the list.
The first complete HuCard pinout!
HuCard Port (For a TurboGrafx 16)
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HuCard HuC6280 Signal Name Function Description
Pin # Pin#
1 -- /CARD_DETECT When connected to ground, tells system
there is a card inserted. TurboDUOs use this to know whether to run the
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