PIC Microcontroller Note

Addicted to electronics, microcontroller, LED Dot Matrix, Led 7-Segment, PIC Digital Clock, Digital Watch, Led Dot Matrix Clock, Led Dot Matrix Watch, GPS and other DIY projects. Short notes about my PIC Microcontroller experiments sometimes it's just a short note sometimes it's a full PIC Microcontroller Project. The information here including source code and schematic are available for FREE, please contact me if you want the source files of the schematics/PCBs.

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.

2 comments:

XmanApril 8, 2009 at 2:09 PM
thank you so much!I was in really big trouble before reading your article!
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Ni@mMay 4, 2012 at 3:19 AM
First of all thanks for the article! Actually it would be much better if you could configure each pin as open drain explicitly.
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