Electrical rules check problem

[Rene_Poschl]

@bobc

It cannot tell if you have several outputs that are enabled by an enable line, which is commonly used by output buffers.

In such a case the output is typically a three state pin, or it is open collector/open emitter. (Open drain/source)
If it is a push-pull output then you can not connect multiple output pins together. (You would need a device in between that does allow an output to float.) If one assigns type output to a pin, KiCads ERC assumes it is a push/pull output.

KiCad has an option for telling ERC about these sort of pins. More details about electrical types see this faq post:

Electrical type of schematic symbol pins (KiCad 4 and KiCad 5)

What are electrical types used for? The electrical type is used by the electrical rule check (ERC) to determine if you made an obvious mistake. ERC is really quite limited. All it does is read all electrical types of pins connected to a particular net and check their combination against the error matrix. Example: By default connecting two output pins together will result in an error. (Makes sense as one output can be high and one can be low resulting in a short circuit between the positive supp…