Sorry, new to KiCAD so decided to place a single 74HC14 in schematic and single 4-pin connector with VCC, GND, sig input and sig output. Also threw in 5 resistors and 5 capacitors to build a simple (stupid) delay line. Was intending to take this design through DRC, netlisting and then layout the PCB.

First surprise, VCC and GND didn't connect to hidden pins on HC14. Read about PWR_FLAG and attached a flag to VCC and another to GND. Great, no more DRC errors. However, upon inspecting netlist output, neither GND nor VCC connects to the HC14.

Inspected pin listing for HC14 and both GND (pin 7) and VCC (pin 14) are listed as PWR inputs.

Hide/display hidden pins has no effect.

Any help will be greatly appreciated. Thanks


1 Answer 1


I suspect you follow an outdated tutorial. The current version of the library luckily has gotten rid of the hidden power pins for the 74xx library (sadly some other logic libs still have them, we simply did not have the manpower during the v5 development phase).

This means the power pins are on a separate unit (for all of them the last unit is the one with the power pins). You need to place that unit and connect the pins like any other pin.

There are good reasons for not allowing symbols with hidden power pins. The main ones are that such symbols are very restrictive as they do not allow for having more than one power supply, and they are unsuited for an environment with strict documentation guidelines. There is not much of a downside so the decision was quite easy to make.

Plus you misunderstand the purpose of the PWR_FLAG symbol. This symobl has no influence on what gets connected to what! It is just a symbol with a single power output pin. That is needed as KiCads ERC ensures that every power input pin is connected to a power output pin (every net with a power input pin must have a power output connected). However, as most designs use generic connectors for the power supply you will need to tell ERC where the supply comes from. So one option is to connect the PWR_FLAG symbol as it then provides the power output for the net it is connected to.

  • \$\begingroup\$ Thank you Rene. I played more this AM and found the last section of th hc14. Tied it up. Works great. I appreciate your feedback and think it is a smart design. In OrCAd, I would dedicate a sheet of the hierecal design to show where power and ground were for each IC. I would then place all decoupling caps on that sheet next to the IC so layout artists knew which ICs I wanted to decouple. Again, what a nice tool ... and I did get the meaning of the power flag after I found the seventh section of this part. I've now played out the board and got adequate manufacturing files. Now I'll read manual \$\endgroup\$
    – John1024
    Commented Jul 23, 2020 at 21:11

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