PIC16F628A - Is it normal or not..?

[MrNobody]

I have built a circuit to display something onto LCD using PIC16F628A using internal crystal..
However, the strange thing that happen is I am able to drive the LCD without supplying any voltage to VDD pin..
I just connect 5V to RA2 and GND to VSS and the LCD begins to display the wordings.

I have check the schematic and the board i constructed and nothing is connected to RA2.

I measured the voltage at RA2 and it is measured to be 5.14V. I also measured the VDD voltage and found it to be 4.33V.

Has anybody encountered the same thing before..?
Is my PIC16F628A faulty or did i make a mistake..?

 

[bananasiong]

Hi,
FYI there is no crystal in the PIC, it's just internal RC oscillator. Maybe the PIC is powered via RA2. Internal MCLR pullup is enabled too?

Don't really get what you mean , 5 V is connected to RA2, and then nothing is connected to RA2???

 

[Nigel Goodwin]

Check the internal structure of a PIC, there are protection diodes from most I/O pins to Vdd and Vss - so if there's no power on Vdd it can be fed from a high I/O pin via the protection diode.

The only 'problem' here is that you shouldn't be feeding power to I/O pins with no supply to the PIC.

 

[MrNobody]

The only 'problem' here is that you shouldn't be feeding power to I/O pins with no supply to the PIC.

Oh.. i see.. thanks..


bananasiong:
sorry for that confusion.. jst a slip of my brain combined with a slip of my fingers while typing..