Thursday, October 16, 2008

Open-Drain RA4 pin on PIC Microcontroller

I had a problem with RA4 pin which I cound not send '1' nor output 'high' to this pin. After some searches, I have found that RA4 pin (pin 3 for PIC16F627a) is "Open-Drain" type output pin. That means it cannot source current and it will be high impedance when assigned logic '1' to it. I cannot set this pin as an output pin by using 'TRISA=0x00'. The solution is attaching a pull up resistor (10K) to the RA4 pin in order to use this pin as an output pin.

RA4 Open Drain PIC16F627a

2 comments:

marian said...

thank you so much!I was in really big trouble before reading your article!

Ni@m said...

First of all thanks for the article! Actually it would be much better if you could configure each pin as open drain explicitly.