# Is it possible that I fried an MCU pin by performing a continuity test

I have a microcontroller (dsPIC33EP64GS506, 64-pin, TQFP, link to its datasheet), which doesn't seem to work on 2 GPIO pins (pins 4:RC0 and 11:RC11), whereas all other pins are functional. The problem with these two pins is that they are directly connected to GND, even when the MCU is not powered. I tested all neighboring pins with continuity check to check for possible short circuits (bridges between pins), using a Fluke 179 multimeter. None of the neighboring pins are short-circuited.

Now, MCU pins are 3.3 V tolerant, and some of them are 5 V tolerant. In the multimeter's User manual, it says that the open circuit test voltage is <8.0 V DC, and the short circuit current is <1.1 mA. Is it possible that I fried the two MCU pins using this continuity test? I have two equal boards, the other one seems to work just fine.

Is it possible that I fried these pins while soldering? I've soldered the MCU on 300 °C with a 2.2 mm tip.

I found the error. It was due to the bad PCB manufacturing - via is connected to the ground plane, and it shouldn't be. See attached image. I've fixed this by cutting the ground plane around the problematic via.

• It seems unlikely that either of these things would damage the micro. It would help if you updated your question with a link to the datasheet and a note of which pins are the problem. – Jack B Nov 18 '16 at 15:16
• It is dsPIC33EP64GS506 MCU, and pins are 4:RC0 and 11:RC11. I've edited the question. It seems that these two pins are directly connected to GND, even when the MCU is not powered. – Marko Gulin Nov 18 '16 at 15:20

• I forgot to mention: The problem with these two pins is that they are directly connected to GND. Even when MCU is now powered. – Marko Gulin Nov 18 '16 at 15:17