What is PIN Direction
When creating a component library in Fusion 360 / EAGLE, you need to create a symbol (part of the electrical schematic).
At this time, you need to set the symbol shape and number of terminals of the part. The item for setting the component terminal function is Direction.
There are nine options for PIN Direction:
| Direction | full name | Types of | Remarks |
|---|---|---|---|
| nc | Not connected | Empty pin | Thermal/fixed pad |
| in | Input | enter | IC input pin |
| out | output | Output | IC output pin |
| io | Input / Output | Two-way | GPIO |
| oc | Open Collector | open collector | IC open collector output |
| pwr | Power Input Pin | Power input pin | IC power pin |
| to | passive | Passive | Resistor/Capacitor |
| speed | high impedance | High resistance | tri-state buffer |
| sup | General Supply Pin | Universal power pin | Power/Ground Symbol |
At the same time, these settings can be used in conjunction with the PIN Function. For the negative-level input pin, select DOT in the PIN Function. For the clock signal input pin, select CLK in the PIN Function. If both are met, select DOTCLK (different from PIN Direction). , the PIN Function only affects the appearance of the pin in the electrical schematic).
The main reason for setting PIN Direction is to allow ERC to detect incorrect connections. For example, if the output pin of an integrated circuit is connected to the output pin of another integrated circuit, ERC will issue an ERROR for the connection. At the same time, the setting here is not only Only generate or not generate ERROR. SUP and PWR behave in a special way, so incorrect configuration can result in connections that don't look like the schematic.
SUP gives wiring the same name
Care must be taken when setting up SUP because it has characteristic behavior that is different from other behaviors. If not set up properly, the circuit may behave differently than it looks. The characteristic of SUP is that no matter how many components with different NAMES are placed, they are always linked to each other.
As written in the table at the beginning, it is assumed that the person using it will use it for power/ground symbols such as GND and VCC (probably).
In an electrical schematic diagram, wires with this symbol represent their interconnections.
It is used to prevent wires from crossing everywhere and improve readability.
Assuming it's used as a pin for an electronic component (which you generally shouldn't do), the problem arises when placing two components.
In time they are not connected in the circuit diagram, but they are actually connected.
Note that if SUP is used as the battery pin, all batteries will be forced to be connected in parallel.
PWR named when not connected
PWR is the power input pin for the IC. It behaves slightly differently than other pins, which are named before being wired on the schematic.
- Looking at the name of the wire on the IO type pin, you will see that it is named N$1. In this state, the two are not connected on the circuit board.
- Force the name of this line to 5V, the same name it had when we created the power pin library, and now the two lines are connected on the board. Although no routing is done to the PWR pin, the connection is still there.
- Next, bring out the wires from the PWR in the schematic. The name of this wire is N$1, and the two connections on the board are broken.