Devices > Implementing Grounds in the Generative Flow

Grounds and Ground Wiring Flow Using Ground Design Functionality

You can use ground design functionality to implement ground devices when creating Capital Logic Designer and Capital Systems Integrator designs in the generative flow. The generative flow is intended to separate the logical connectivity requirements (in Capital Logic Designer designs) from the physical constraints and implementation (in Capital Systems Integrator designs).

Caution

For an overview of the possible ground device flows and the differences between them, see Implementing Grounds in the Generative Flow.

When creating logical designs, you specify that a device needs to be grounded but you do not need to know where in the vehicle each device is grounded. You specify the locations of the ground devices in the associated Capital Systems Integrator designs).

A ground device can have any number of pins.

Note

When using this flow, you do not share a ground device in Capital Logic Designer.

There are three stages to using ground design functionality in Capital Systems Integrator:

Setup You must develop logical designs and Capital Systems Integrator constraints in such a way to support the ground design process.
Placement After placing all non-ground devices in Capital Systems Integrator, you place the ground devices.
Combination An important capability within ground design is to combine the individual logical grounds so that specified ground signals can share wiring.

These stages are explained in greater detail in the following sections:

Setup

In Capital Symbol Designer:

Create one or more ground symbols in Capital Symbol Designer. See Creating a New Symbol in the Capital Symbol Designer User Guide.

Note

The starter data supplied with the software includes symbols for grounds in the Quick Start - Electrical symbol library.

In Capital Logic Designer:

Add ground devices to a design and connect them to devices that require grounding. It is normally most efficient to use a separate ground device for every single pin that needs to be grounded. In the case that you know that two or more pins must be connected to the same ground point, you can use a single ground device. However, connecting large numbers of pins to the same ground device adversely affects the performance of ground placement in Capital Systems Integrator and is undesirable. You can create a ground device in Capital Logic Designer only by adding a device with a ground symbol. You cannot convert an existing device in a design to a ground device nor can you convert a ground device to a normal device. See Adding a Device from Capital Component Manager in the Capital Logic Designer User Guide.
Properties are typically used to drive the specification of Capital Systems Integrator constraints that control the placement and combination of ground devices. A strategy for this should be determined before any significant design work is done and the appropriate properties assigned to the ground devices. It may be most efficient to use a small number of different ground device symbols which are pre-populated with the appropriate properties. Typically, one property is used to drive placement of grounds and at least one more used to drive combination. For example, you could use a Ground type property (using values such as Engine and Body) to control placement and a Ground class property (using values such as A and B) to control combination.

In Capital Systems Integrator:

Specify which slots in Capital Systems Integrator designs contain ground devices that you added to the associated Capital Logic Designer designs. You do this by specifying a Slot Type of Ground in a slot’s properties. Note The best way to represent multiple ring terminals connected to a single ground stud is to add multiple slot connectors to the ground slot. Each slot connector represents a potential ring terminal and should have a single cavity. This should be enforced using the Max Ground Slot Connector Cavities constraint: Maximum cavities per ground slot connector is 1.
Assign ground refinement constraints to objects in the Capital Systems Integrator design that control the placement and combination of ground devices. The “Place by Attribute/Property” constraint is used to control the placement of ground devices. For a list of the constraints that control the combining of ground devices, see “Ground Refinement” in the Overview of Rules and Constraints section.

Placement

of Ground Devices

Note

Before placing ground devices in Capital Systems Integrator, it is essential that most (if not all) non-ground devices are placed. If you have a license for optimized ground placement, it relies on this information to calculate the optimum placement slot for each ground device.

Place the ground devices in ground slots in Capital Systems Integrator. You can either:

Manually place individual ground devices.
Have the system place ground devices. The result of this depends on whether you have a license for Optimized Ground Placement.

See Placement of Ground Devices in Slots for details of both.

Combination

If multiple ground devices are placed (either manually or automatically) in the same ground slots, this results in separate ground trees running from each grounded device back to the connected device in the ground slot. It is therefore desirable to combine these ground devices which can then share wiring with fewer signals. This is done before routing signals.

When you combine ground devices, any constraints on the slot are taken into account.

You can combine ground devices in two ways: By manually combining selected ground devices in a slot and editing the signal map of the slot. See Combining Normal Devices in a Slot.

By automatically combining ground devices in ground slots. See Combining Ground Devices in All Ground Slots or Combining Ground Devices in Selected Ground Slots. Note Generally, slot connectors have one cavity. However, if you have slot connectors with multiple cavities, the following applies: In both cases, signal mappings are re-balanced across existing slot connectors and their cavities taking into account the Max multitermed Ground Signals constraint. New cavities may be generated on existing slot connectors as a result of the constraint as long as the new cavity does not violate a Max Ground Slot Connector Cavities constraint. Once the maximum number of cavities is reached on a slot connector, the remaining signal is multi-termed regardless of any Max multitermed Ground Signals constraint. This may result in cavities having too many terminations because you cannot add more cavities to a slot connector. If you run the “Ground device that breaks placement rule” design rule check, this informs you of any cavities with too many terminations and you can make changes to the design to fix these.

After you have placed and combined ground devices in slots, you may want to remove any unused connectors and cavities that the process has created. See Removing Unused Connectors, Holes and Cavities from Slots.
After placing devices in slots and routing signals, you may want to add wire connections between cavities in ground slots. It is sometimes a requirement to protect against the failure of a ground point (that is, where a weld fails and the ground stud is no longer attached to the chassis). This is often achieved by adding additional wires between the ground points themselves. These wires are not based on any net conductor connection in the functional design from Capital Logic Designer. You cannot add wire connections like this between equipment slots (even if ground devices are placed in the equipment slot). See Adding a Wire for more information about adding wires.

Parent Topic:

Implementing Grounds in the Generative Flow