16F690 oddities

Community General Discussions
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1

So apparently pin 11 can be used as Vdd and pin 10 as Vss?

so I accidentally plugged in my PIC backwards in my circuit on my bread board. When the led didn't light (it was supposed to blink), I assumed I got the code wrong and had the led connected to the wrong pin, so I plugged the led in different placed until the led flashed, then I realized it was the right pin, just wrong side.

Is the chip smart enough to figure out what I want as input voltage? If the pins can be used as power source and ground, why isn't it listed as such in the data sheet?

2

A Guess

At a guess, I’d say that the differential between the unused IO pins and the +V may be what’s JUST ABOUT providing enough power for the application to run. Remember that +5V is not always +5V. It’s only +5V RELATIVE to your 0V.

This feature is documented elsewhere on the Microchip website and, in fact, some in-circuit serial programmers employ of it. Personally< i wouldn’t rely on it I think it’s a bit of an accident of the design.