Post by thread:Interfacing two PICs

Hi, This may be an elementary question but I am drawing a blank. All I want to do is connect a pin on a basic stamp that is configured as an output to a pin on a PIC16C84 that is configured as an input. Do I have to do anything other than just tie these two together? Does there need to be any resistors involved. Thanks in advance. Troy Powledge spam_OUTtpowTakeThisOuTeramp.net ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Kitty Powledge Certified BeautiControl Image Consultant http://www.eramp.net/bcontrol/ .....tpowKILLspam@spam@eramp.net ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

You only need a resistor if there might ever be a time when both pins are outputs (and thus trying drive the line at the same time) the resistor limits the current to safe levels. Since the 16C84 is programmed as an input you don't need a resistor. --Chuck ---------- From: Troy Powledge[SMTP:tpowKILLspamERAMP.NET] Sent: Sunday, September 22, 1996 11:23 AM To: Multiple recipients of list PICLIST Subject: Interfacing two PICs Hi, This may be an elementary question but I am drawing a blank. All I want to do is connect a pin on a basic stamp that is configured as an output to a pin on a PIC16C84 that is configured as an input. Do I have to do anything other than just tie these two together? Does there need to be any resistors involved. Thanks in advance. Troy Powledge .....tpowKILLspam.....eramp.net ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Kitty Powledge Certified BeautiControl Image Consultant http://www.eramp.net/bcontrol/ EraseMEtpowspam_OUTTakeThisOuTeramp.net ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Troy Powledge wrote: > > Hi, > This may be an elementary question but I am drawing a blank. All I want to > do is connect a pin on a basic stamp that is configured as an output to a > pin on a PIC16C84 that is configured as an input. Do I have to do anything > other than just tie these two together? Does there need to be any resistors > involved. > > Thanks in advance. > Troy Powledge > tpowspam_OUTeramp.net > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > Kitty Powledge > Certified BeautiControl Image Consultant > http://www.eramp.net/bcontrol/ > @spam@tpowKILLspameramp.net > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Kitty, I don't know about the 16C84, but according to Parallax when a basic stamp is configured to output on an I/O, it acts like a switch between power supply rails! A 'high' is equal to being connected to the +5VDC rail, and a low is equal to being connected to ground! Since the I/O's only sink 25 mA, and source 20 mA, it could be very possible to blow your stamp's onboard voltage regulator! (or Worse, kill the stamp's PIC!) I would assume the 16C84 has this same type of 'Totem Pole' output, and if so, you could seriously damage it as well!. For a simple solution, put a 10 K resistor inline between the I/O's. Voltage highs and lows will still be 'felt' by the stamp. (and probably the PIC also!) One other note. The stamp may sink and source 25/20 mA per I/O, but the whole stamp (total of all pins) can only source 40 mA, and sink 50 mA! -Calladus- KILLspamcalladusKILLspamix.netcom.com

{Quote hidden}> > Troy Powledge wrote: > > > > Hi, > > This may be an elementary question but I am drawing a blank. All I want to > > do is connect a pin on a basic stamp that is configured as an output to a > > pin on a PIC16C84 that is configured as an input. Do I have to do anything > > other than just tie these two together? Does there need to be any resistors > > involved. > > > > Thanks in advance. > > Troy Powledge > > RemoveMEtpowTakeThisOuTeramp.net > > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > > Kitty Powledge > > Certified BeautiControl Image Consultant > > http://www.eramp.net/bcontrol/ > > spamBeGonetpowspamBeGoneeramp.net > > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > > Kitty, I don't know about the 16C84, but according to Parallax when a > basic stamp > is configured to output on an I/O, it acts like a switch between power > supply > rails! A 'high' is equal to being connected to the +5VDC rail, and a > low is equal > to being connected to ground! Since the I/O's only sink 25 mA, and > source 20 mA, it > could be very possible to blow your stamp's onboard voltage regulator! > (or Worse, kill > the stamp's PIC!) I would assume the 16C84 has this same type of 'Totem > Pole' output, > and if so, you could seriously damage it as well!. > For a simple solution, put a 10 K resistor inline between the I/O's. > Voltage highs > and lows will still be 'felt' by the stamp. (and probably the PIC also!) > > One other note. The stamp may sink and source 25/20 mA per I/O, but > the whole stamp > (total of all pins) can only source 40 mA, and sink 50 mA! Um, I think the switch between power rails simply means the I/O is CMOS which switches to very near the rails anyway. If the two parts are on the same board, a simple wire should be fine. BAJ > > -Calladus- > TakeThisOuTcalladusEraseMEspam_OUTix.netcom.com >

> From: Troy Powledge <RemoveMEtpowTakeThisOuTERAMP.NET> > This may be an elementary question but I am drawing a blank. All I want to > do is connect a pin on a basic stamp that is configured as an output to a > pin on a PIC16C84 that is configured as an input. Do I have to do anything > other than just tie these two together? Does there need to be any resistors > involved. Just tie them together. It's as simple as connecting a CMOS output to a CMOS input. Since the PIC starts up with all ports configured as inputs there is no possibility of connecting two outputs so long as your code in the 'input' PIC doesn't set the TRIS bit to a zero (output). Regards, SJH Canberra, Australia