How to use RA4 as an output pin in 16F648A mcu

arunb · Joined: 08 Sep 2003 Posts: 492 Location: India

Hi,

I am not able to use the RA4 as an output pin in a 16F648A mcu, kindly explain how I can do this ???

thanks
arunb

Ttelmah · Guest

Look at the pin diagrams in the data sheet.
RA4, functions as an output, _but has no pull up FET present_. Hence _you_ must pull any line attached up externally with a resistor etc..

Best Wishes

Guest · Posted: Wed Oct 04, 2006 7:16 pm

Hi,

Actually, RA4 has an output FET, but it is open-drain. You solution, however, is correct.

Ttelmah · Guest

Read what I say.
It has no _pull up_ FET. The normal outputs have two FETs, one a P type, connected to the Vdd rail, and the other an N type, connected to Vss. Both are wired as 'common source' devices (with their sources connected to their respective supply rails). A4, has the P type (pull up) FET omitted.

Best Wishes