The Electrical Rules Check tries to ensure that everything that is connected to a single net fits together. The quick summary is that a valid net has
- either power (
power_in
, power_out
) or data (input
, bidi
, output
) pins, not a mixture of them
- at least one pin that can drive the net (
power_out
for power nets, bidi
or output
for data nets)
- at most one pin that unconditionally drives the net (
power_out
or output
)
So a power network needs exactly one power_out
connected to it.
A known limitation is that connectors' pins are defined as passive
, because that doesn't immediately lead to a conflict with anything else connected to the same net, so the connector that the power supply is connected to cannot be marked as having a power_out
pin to placate the ERC.
The PWR_FLAG
pseudo-component provides a single power_out
pin, so you can avoid the warning here. The ERC will complain if the same net has two PWR_FLAG
s, or a PWR_FLAG
and some other component with a power_out
pin (such as a linear regulator).