Also tie the mclr to + 5v supply through a resistor or directly, it does not like to be floating Zack E-Mail: spazzman@iname.com One regrets more the things that you did not do than the things you did do. -----Original Message----- From: Jim Paul To: PICLIST@MITVMA.MIT.EDU Date: 01 May 1999 06:48 Subject: Re: 16F84 PROBLEM >Graham, > >I would add a 10uF and a .1 uF cap between Vdd and Vss at the 'F84'. >Also, I would enable the weak pullups on Port B as well. That is unless >you already have done these things. Also, make sure the watchdog timer >is not tripping you up. I don't think the W/D timer is the problem from >what >you state is happening. You may want to check the 5 volt regulator to make >sure it is functioning properly also. What kind of oscillator are you >using? >Are you using a crystal or canned Osc? Do you have the power up timer >and the Osc startup timer activated? If not, the part may not be getting >a good clock signal before it starts running. Just some things to check. >Hope this helps. Also, I'd like to know what you did to fix it when you >get it >fixed. > > >Regards, > > >Jim > >-----Original Message----- >From: Graham >To: PICLIST@MITVMA.MIT.EDU >Date: Saturday, May 01, 1999 11:31 AM >Subject: 16F84 PROBLEM > > >>I'm working on a little PIC project and out of sheer desperation I am >>appealing to you for help! >> >>I've designed a very simple alarm system for my house using the >>PIC16F84, that uses Change on Port B Interrupt to detect whether a door >>or window has opened. It then actuates a relay for an alarm and flickers >> >>an LED to indicate on a diagram where in the house it was. >> >>Simple to design and program using MPLAB, but when I burn it in and test >> >>it, I find that it is VERY erratic. For instance when I apply power >>(5.05v through a regulator) some LEDs flash spontaneously that are NEVER >> >>supposed to flash and it acts strange. Normally when I then >>apply Master Reset it resets properly and works fine, but not always. >>Sometimes when reset it acts the same as during a power up. >>Even when I think it IS working fine it sometimes does strange things >>inconsistently. >> >>I've even simulated a Power-On reset and it starts up properly in MPLAB. >> >>BTW I've combed through the source code and everything looks fine also >>in simulation. >> >>It would be really great if you could give me some tips please. I use >>12.45v to program it (unregulated) and 5.05v (regulated) for Vdd. I use >>a 4MHz crystal and power up timer on, watch dog off. >> >>Could the PIC be damaged? Why is it erratic? >> >>Thank you! >>Graham. >