Post by thread:[PIC]: 877 + portC

Hello, if i use PortC of the 16F877 as a "normal" output do i need to add an extra pull up resistor? (just like Ra.4 of the 16F84, this is also a ST-buffer ) Thanks, Aart. -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics

>Hello, > >if i use PortC of the 16F877 as a "normal" output do i need to add an extra >pull up resistor? >(just like Ra.4 of the 16F84, this is also a ST-buffer ) > >Thanks, >Aart. No, Ra.4 of the 16F84 is open drain. PortC of the F877 is not. Bob Ammerman RAm Systems (contract development of high performance, high function, low-level software) -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics

> if i use PortC of the 16F877 as a "normal" output do i need to add an > extra pull > up resistor? (just like Ra.4 of the 16F84, this is also > a ST-buffer ) You could have easily found this answer in the data sheet if you had looked. Page 33, section 3.3 "PORTC and the TRISC Register" clearly documents port C as having totem pole outputs. So no, you don't need a pullup resistor. ******************************************************************** Olin Lathrop, embedded systems consultant in Littleton Massachusetts (978) 742-9014, spam_OUTolinTakeThisOuTembedinc.com, http://www.embedinc.com -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics

> >if i use PortC of the 16F877 as a "normal" output do i need to add an >extra > >pull up resistor? > >(just like Ra.4 of the 16F84, this is also a ST-buffer ) I think you are confusing Schmitt Trigger with open-drain. Open-drain pins require a pull-up to function as you cannot drive them high from the PIC. PORTC of the '877 has no open-drain pins, so you don't NEED pull-ups. You can still use them, though, if your application requires it (i.e., using an SPST pushbutton for input, pulled high, or for I2C communication). --Andrew _________________________________________________________________ Get your FREE download of MSN Explorer at http://explorer.msn.com -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics

Hello Aart, >if i use PortC of the 16F877 as a "normal" output do i need to add an extra pull up >resistor? it's a "normal" output. Regards, Brusque ----------------------------------- Edson Brusque Research and Development C.I.Tronics Lighting Designers Ltda (47) 323-2685 / (47) 9993-6453 Blumenau - SC - Brazil http://www.citronics.com.br ----------------------------------- -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics

>if i use PortC of the 16F877 as a "normal" output do i need to add an extra pull up resistor? >(just like Ra.4 of the 16F84, this is also a ST-buffer ) No resistor needed, portC has normal outputs. One thing I noticed yesterday, when used as inputs, not all the inputs on portC have the same thresholds. RC0 had 0/1 thresholds of 1.8 and 2.65 volts. RC4 had thresholds of 2.1 and 2.5 volts. PIC was being supplied 5 volts. Cheers, Bob -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics

Thank you all for the replies, yes i read the datasheet carefully still didn't know for sure. Since i'm designing the pcb i'd rather be a 100% sure. Thx !! Aart. > > if i use PortC of the 16F877 as a "normal" output do i need to add an > > extra pull > up resistor? (just like Ra.4 of the 16F84, this is also > > a ST-buffer ) > > You could have easily found this answer in the data sheet if you had looked. > Page 33, section 3.3 "PORTC and the TRISC Register" clearly documents port C > as having totem pole outputs. So no, you don't need a pullup resistor. > > i get tired to scroll down every message so i prefer to anwser on top.. -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics