Posted By
dmantione
on 2022-12-07
15:14:03
|  Re: External User Port for the C16: Let's make it!
The secret to the 6529 is its "Weak pull-up" behaviour: If you set it high (transmit a 1), the line is pulled up with +- 8 kOhm. This resistance is low enough for reliable communication as an output, but high enough so that it can easily be overridden by a transmitting device when used as an input.
As long as a pin is high (you are sending a 1), you can also read from the pin.
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