Regards Clive Frederickson R&D Technician (CECF Group) ---------- From: Clive Frederickson Sent: 04 May 2001 12:04 To: 'Andrew Errington' Subject: RE: [PIC]: P16F84 'A' Fun and Frolics Hi Andy Thanks for responding. I follow what you are saying about the code. I do normally fully document my code and use labels etc. And I also know that this code works fine, as does my original code. Also it is definitely not wiring (these have been checked, rechecked, double checked etc....) Basically the PIC16F84 works fine, the 84A does not. The 84A only gets upset if a decoupling capacitor is fitted to the input pin. It is fine when the cap is removed. Being an high impedance input, I would of thought the cap would not have an effect on the pic, but only on the voltage level present at the input. The decoupling cap does not effect any of the other input pins, only RB3. It is a weird fault. Its not a problem in that I can loose the cap and improve my de-bounce in software (which I have done). But I am concerned that the apparent fault is a result of more underlying problems, Either with just my pic's or 84A's in general. I am trying to speak to Microchip tech guy's, Who knows they might just be able to help. The programming problem as been resolved by increasing my Vpp to just over 13v. But I think the cause is down to a insufficient reservoir cap. I shall look into this in time. Still, Nothing like a challenge to inspire one self. Have a good bank holiday Thanks again. Regards Clive Frederickson R&D Technician (CECF Group) ---------- From: Andrew Errington [SMTP:ame@synaptics.com] Sent: 03 May 2001 18:48 To: Piclist Cc: Clive.Frederickson@DYSON.COM Subject: RE: [PIC]: P16F84 'A' Fun and Frolics Hi, > The code below was written deliberately without using include > files, labels > definitions etc, I disagree that that makes any sense. Using symbols is a way to guard against typos and oversights when writing (or more importantly, changing) the code. If you are concerned about the form of the final output you only have to look at the hex in the listing file. > I started with a working program that was using include files, > macro etc. A > program that has been in use in over 200 finished units that have been > working happily for up to 3 years (so far). This same code in the same > circuit using an A revision chip fails to function correctly. I > ended up the > simple code to prove it was not me but the PIC. (I was convinced it was me > and did everything I could to prove it was not before settling for the PIC > as the cause.) According to Microchip's data sheet for the PIC16F84A the only differences noted (Table B-1 in Appendix B) are: 1) Max voltage is now 5.5V, but top temperature +125degC 2) Max frequency increased to 20MHz 3) EEPROM cycle faster 4) Rext range starts at 3kohm None of these should be affecting you, and your code looks simple enough and ought to work. Is there a "16F84A" option for the list directive? (The Microchip web site does not remark upon updates for MPLAB for PIC16F84A) How about a wiring error on your board? Perhaps by shorting RB3 to ground you are inadvertently causing a brownout. Perhaps the original chip is not as sensitive to this as the 'A' version is. I would try this myself, but I do not have any of these chips. Good luck, Andy *-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-* The new Dyson Root8Cyclone(TM) vacuum cleaner is the most powerful upright available. See this new technology at http://www.rootcyclone.com Like all Dyson cleaners the Root8Cyclone(TM) maintains constant suction. Dyson scientists have developed the Root8Cyclone(TM) to give higher suction power and pick up more dust. It will be available from June 2001 in the UK. *-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-* -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.