Thanks for your replies Carl and Andy. Speaking for myself, I have designs that use two instances of the same micro, with each instance on a different supply rail. These micros all have a power pin named VCC and I have no problems with ERC, so Kicad isn't covertly connecting my VCC pins together.
The OP (Mark) wants to have logic chips on two different supply rails, but it seems that Kicad joins up all the hidden pins marked Vcc, even if you connect the power pin to a different rail. Is the critical factor that the pins are hidden, is it that the name case sensitive, or is it a feature of multi-part components? It's not that the pin doesn't have a number, because the logic chip symbols have both name and number specified for the power pins (like the symbols I have created for myself). What is the critical thing that Mark has to change to allow him to connect two logic chips to two different supply rails. Regards, Robert. On 16/03/2010 11:14, Andy Eskelson wrote: > Vcc IS the power to the chip, U2A in this case. > so why have you connected +5V to it as well? > > DRC is detecting that you have effectively shorted VCC to a different 5V > supply as well, and is complaining about it. > > Power flags are defined as power out pins, and you only have one power > out on a power net,m if you add a second power flag DRC will complain > about that as well. > > I think you are assuming that you need to connect 5 volts to the chip, > and so are adding the +5V port, which is another independent supply net. > Hence the confusion. > > The system works as has been mentioned by the power port names. When a > device has a power pin with a specific name, AND you set the pin to be > invisible you DO NOT need to connect anything else to it. As soon as you > put a power port with the same name onto the circuit diagram, that port is > automatically connected to all device power pins with the same name. > > > A power net needs to be energised or DRC will complain. That can be done > in two ways. Either a device such as a regulator can have a power out > pin, which will indicate that it is energised, OR you add a power flag, > which simply says that the net is energised. You use power flags in > situations where you are connecting an external power source to your > circuit via a connector, flying leads and so on. > > The one oddity is that GND is considered a power out type net as well, so > it also needs energising with a power flag. > > logic IC's have generally had their power pins identified by names > rather than the voltage, so you have Vcc Vss Vdd and so on. > > When you run into such chips, the same will apply, power ports of the > same name are already considered to be connected to the physical supply > > Andy > > > > > > On Mon, 15 Mar 2010 16:13:15 -0000 > "mtheling"<p...@swapout.de> wrote: > >> Hi Robert, >> >> if I connect for example a net "+5V" to a component U2A which has an VCC >> input as invisible pin, I see that in PCBnew the pin is connected to the >> "+5V" net as soon as I set an Powerflag to +5V. >> But the ERC check in eeschema states this as error : >> ErrType(5): Conflict problem between pins. Severity: error >> @ (5,1000 ",6,7500 "): Cmp #FLG01, Pin 1 (power_out) connected to >> @ (4,4000 ",6,7500 "): Cmp #FLG06, Pin 1 (power_out) (net 3) >> >> If I don't connect a Powerflag to the "+5V" net, in PCBnew the Power Pin of >> U2A is still connect to the VCC net and not to "+5V" as set in the schematic. >> Please see schematic for example: >> http://www.swapout.de/example_schematic.pdf >> >> What I am doing wrong? >> >> Thank you, >> >> best Regards, >> Mark >> >> >> >> >> ------------------------------------ >> >> Please read the Kicad FAQ in the group files section before posting your >> question. >> Please post your bug reports here. They will be picked up by the creator of >> Kicad. >> Please visit http://www.kicadlib.org for details of how to contribute your >> symbols/modules to the kicad library. >> For building Kicad from source and other development questions visit the >> kicad-devel group at http://groups.yahoo.com/group/kicad-develYahoo! Groups >> Links >> >> >> > > > ------------------------------------ > > Please read the Kicad FAQ in the group files section before posting your > question. > Please post your bug reports here. They will be picked up by the creator of > Kicad. > Please visit http://www.kicadlib.org for details of how to contribute your > symbols/modules to the kicad library. > For building Kicad from source and other development questions visit the > kicad-devel group at http://groups.yahoo.com/group/kicad-develYahoo! Groups > Links > > > > > > > No virus found in this incoming message. > Checked by AVG - www.avg.com > Version: 9.0.790 / Virus Database: 271.1.1/2749 - Release Date: 03/15/10 > 19:33:00 >
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