Without wishing to sound negative, this technique is incredibly risky at best. There is absolutely no guarantee that the two PICs are synchronised together. The Power On Reset voltage of the PIC is not exact, one is bound to come out of reset before the other. If the Power-up Timer is used, this is based on an internal RC oscillator, and will vary between PICs. All this means that the PICs could be running the same program, but not always the same instruction at the same time, with obvious consequences. As a quick hack to get more output current, it obviously worked for you, but an external driver of some description would be a more reliable solution. Regards Mike Rigby-Jones (whose NOMAIL command to the listserv obviously didn't get through and who has just waded through 604 mails after a week out!!) > -----Original Message----- > From: tony kathro [SMTP:anthonyk@NETSPACE.NET.AU] > Sent: Monday, August 16, 1999 2:43 PM > To: PICLIST@MITVMA.MIT.EDU > Subject: Parallel Pics > > As a newbie to Pics I have followed the list for some time via the > Iversoft > archive. My first project worked fine after some serious learning > experiences. But I was left a little short in the drive capability area. > Before building some driver circuitry I thought I might try the > unconventional approach. I placed two Pics 16F84 in parallel, pin for pin, > except the 10Mhz OSC out of the first Pic went to the OSC in on the second > Pic. Both chips had the same progamme burnt in. My programme is some 300 > lines of (newbie) code with TOCK being used as a 32,768 input and RB0 used > as an input also. The outputs are 11 Leds each at the 60 ma. level. > Clearly > I expected this to work and to my suprise it did. It has now run non-stop > for a week, no smoke out of the Pics and the programme does everything I > intended it to. > Question. Is this a serious case of mind over matter or have I found > something which might be of use to some of you. (Pardon. ..some of US) > For those brave souls with more Pics than sense, an easy way to place the > chips in parallel is to remove pin 15 from the cheaper variety of 18 pin > socket, splay the pins slightly and gently press over your 16F84. Most > important to line up the indicating marks so that you know which end of > the > Pic is which. It helps if this chip is in a turned pin socket and clamped > for the next operation. You will see that each solder pin of the socket > sits > neatly over the shoulder of the Pic pins. Deep breath and solder all pins > to > shoulders EXCEPT pin 16. Gently bend this pin until you can solder it > to > the shoulder of pin 15 of your PIC. A gentle touch and a fine solder bit > makes this easy. You now have a Pic sandwich with nice turned pins to > plug > into your application/programmer and a somewhat dubious socket on top to > accept the second Pic. > Those of you with a Dontronics DT001 will now find that you can programme > both chips at the same time.(Very happy with mine) Your mileage may vary > according to your own setup. > Can I stress that this Kluge does work on my software but that I lack the > knowhow to even guess if it will be of use to anyone else. I think that > perhaps after such a long first post I should now sink back into obscurity > and continue my lurking. > Have fun and consider the likely pushing and shoving in the ranks if your > Pics do not have the same programme.!!! > > TK