About ports

Ports export nets from a module to the higher-level schematic and define connection points for wiring signals. Modules organize hierarchical schematics by creating sub-designs on separate sheets.

Ports and Port Instances

Each port belongs to a Module. When you add a port to a module, a corresponding Port Instance is created on every instance of that module in the schematic.

Port — defines the name and direction of the connection. The direction controls signal flow for the Electrical Rule Check (ERC): io, nc, in, out, oc, pwr, pas, or hiz.
Port Instance — the object you select and interact with in the canvas. Changes to a Port Instance — including side, position, and direction — apply to all instances of the module.

Working with Port Instances

Port Instances behave like other selectable objects in the schematic:

Inspector — select a Port Instance to view and edit its properties in the Inspector panel.
Context menu — right-click a Port Instance to access Move, Delete, Mirror, and Rotate actions, as well as Properties.
Direct drag — drag a Port Instance to reposition it without invoking a command.
Design Manager — Port Instances appear as items under their module in the Components view.
Selection Filter — use the Selection Filter panel to filter by Port Instance type.

Copy and paste do not apply to Port Instances. To add a port, use the Add Port command.

Bus ports

A bus port exports an entire bus through a module boundary, allowing the parent sheet to connect to the bus as a single unit. Bus ports support simple buses (like DATA[0..7]) and complex buses with mixed signal types (like BUS:CLK,DATA[0..7],ENABLE).

When you create a bus port, the port name matches the internal bus specification by default.

Bus port compatibility and visual indicators

Fusion matches bus ports by signal structure rather than exact names. Two buses are compatible when they have the same number of members and matching signal counts:

BUS:A,B,NET[0..5] and SUB:D,E,TEN[0..5] (3 members: 1+1+6 signals)
NET[0..19] and BUS:TEN[1..20] (1 member: 20 signals each)
A,B and D,E,F (incompatible: member count 2 does not match 3)

Visual compatibility feedback appears as you connect buses to ports:

O symbol on the port tip: compatible bus connection; structures match
X symbol on the port tip: incompatible bus connection; structural mismatch
Snapping circle: appears when you draw a bus near a compatible port

Valid O indicator and invalid X indicator on a port tip

The O/X indicator also updates when you adjust the mapping in the Inspector after connecting the bus.

Note: Fusion can connect buses with different names when the signal structure matches. For example, an I2C bus inside a module can connect to a CAN bus on the parent sheet if both buses have the same number of signals. Review the mapping in the Inspector to confirm the pairing matches your design intent.

Default bus mapping behavior

When you connect compatible buses to ports, Fusion automatically creates a mapping between internal nets (inside the module) and external nets (on the parent sheet):

Internal and external net names are sorted alphabetically within their respective buses
Nets are paired by position within matching signal count groups
The mapping happens automatically when you connect the bus

Even compatible buses may need mapping adjustments. Always check the Inspector after connecting buses to verify the net pairing is correct for your design intent.

Adjusting bus mappings

To review and adjust the mapping, use the Inspector Bus Mapping section. See Adjust bus port mapping.