Post by thread:GP3 as output

I remember VERY recently that there was an app note or tech brief on how to make pin GP3 on a PIC12C part to act as an output. Does anybody know where I saw that? Pleeeease? The idea is basically to use turn the pull-up feature on and off, using that to switch a transistor on and off. Thanks! Andy ================================================================== Montana Design Tech Support - http://www.montanadesign.com ==================================================================

In a message dated 5/4/99 8:09:41 AM Pacific Daylight Time, spam_OUTsupportTakeThisOuTMONTANADESIGN.COM writes: << I remember VERY recently that there was an app note or tech brief on how to make pin GP3 on a PIC12C part to act as an output. Does anybody know where I saw that? Pleeeease? The idea is basically to use turn the pull-up feature on and off, using that to switch a transistor on and off. Thanks! Andy ================================================================== >> Hi Andy, It was in the microchip App notes. I have seen it too. I think I could find it again if you can't. I think it was in the design contest section. The problem I remember with this approach was the response time. It would work if your intent is turn on and off a LED, light or sprinkler valve, but it is useless for doing PWM or somthing that requires timeing less than a second. It used an external transistor to detect the presents of the weak pullup on that pin. You can effect an output by turning on and off the pullup for that pin. Regards Dave Duley

> ================================================================== >> >Hi Andy, >It was in the microchip App notes. I have seen it too. I think I could find >it again if you can't. I think it was in the design contest section. >The problem I remember with this approach was the response time. It would I'd appreciate if you could find it. I want it for the SCL line on a EEPROM. Andy ================================================================== Montana Design Tech Support - http://www.montanadesign.com ==================================================================

Hi Andy, GP3 cannot be set as output. What they use is a trick by enabling/disabling the pull-ups and adding a buffer in front of it. regards, Reggie -- e-mail: .....rberdinKILLspam@spam@bigfoot.com ICQ#: 31651436 URL: http://www.bigfoot.com/~rberdin Andy Kunz wrote: {Quote hidden}> > > ================================================================== >> > >Hi Andy, > >It was in the microchip App notes. I have seen it too. I think I could find > >it again if you can't. I think it was in the design contest section. > >The problem I remember with this approach was the response time. It would > > I'd appreciate if you could find it. I want it for the SCL line on a EEPROM. > > Andy > > ================================================================== > Montana Design Tech Support - http://www.montanadesign.com > ==================================================================

At 07:20 AM 5/5/99 +0800, you wrote: >Hi Andy, > >GP3 cannot be set as output. What they use is a trick by >enabling/disabling the pull-ups and adding a buffer in front of it. Yes, I know, what I'm looking for is the app note which described the process as it had some technical data on the internals of the chip wrt the pin. Andy ================================================================== Montana Design Tech Support - http://www.montanadesign.com ==================================================================

> >GP3 cannot be set as output. What they use is a trick by > >enabling/disabling the pull-ups and adding a buffer in front of it. > > Yes, I know, what I'm looking for is the app note which described the > process as it had some technical data on the internals of the chip wrt the > pin. > > Andy > Well Andy ... A quick search through the Microchip web site revealed this URL: http://www.microchip.com/10/Appnote/Category/12CXXX/conApps/5_004/index.htm Ian C.

>Well Andy ... >A quick search through the Microchip web site revealed this URL: >http://www.microchip.com/10/Appnote/Category/12CXXX/conApps/5_004/index.htm Glad it was quick for you. Spent an hour there yesterday (and on CD) and never did find it. They need Mot's search engine. Andy ================================================================== Montana Design Tech Support - http://www.montanadesign.com ==================================================================