Hello, everyone.
  First off, let me just say this list seems to be a wonderful resource.  I 
signed up a few weeks ago, have read the archives quite a bit, and have 
watched the ongoing discussions, and am convinced that all of you have a 
really good thing going here.
  I'm working on my first real project with a PIC right now -- mostly I work 
with linear audio stuff, and the logic functions I've needed I've taken care 
of with 4000 or 74HC series discrete chips, which has begun to get really 
cumbersome.  Hence the PIC, which has so far been powerful and great.

And just so everybody knows, I looked this up in the archives, the device 
datasheet and the mid-range manual first.  So forgive me if these questions 
are silly.

My questions:

1.)  I'm using a PIC16F872.  Sending the MCLR pin low on this device should 
always be a hardware reset, right?  There's no MCLRE config bit on this PIC, 
so that pin is always MCLR, right?  This means that the program counter 
should go to zero, correct?  Which means that if all the registers are 
cleared at the beginning of the program, they should show up reset to 0x00, 
right?

2.)  I'm making a dozen PCBs or so for this project, and so I want to make 
sure all my code is right first, and especially all my hardware layouts.  As 
such I've been running the MPsim on everything in MPLAB IDE 6.6.  I've 
gotten these doubts about MCLR because I've been using the pin stimulus 
function to set it low and then high (both while the program is running and 
while paused -- so I don't think it's a pulse witdth problem) and nothing 
seems to reset at all.
  Do I have something wrong?  Is this a simulator issue?  A chip can't 
ignore a hardware reset, can it?  Do I need to breadboard this?

3.) The actual physical mechanism I have drawn up to trigger this reset is a 
NO momentary pushbutton connected to ground on one side and MCLR on the 
other, with MCLR tied to VDD through a 10k resistor.  I've read on your list 
that it's a good idea to put a 220ohm or so resistor line with the MCLR pin 
-- similar to the way you'd protect the gate of a MOSFET.  Is this true?

Forgive me if these questions are silly or this post is too long.  But I 
sure do appreciate you taking the time to look at this and look forward to 
your replies.

Thanks so much,

Todd Bailey


_______________________________________________
http://www.piclist.com
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist