Creating a Signal bus

Bus creator

Signal Bus

The constituents of a signal bus

A signal bus consists of two mandatory objects:

• A creation point, which can be defined by using a Bus Creator component.

• An extraction point, which can be defined by using a Bus Selector component.

Optionally, a signal bus can be split and "consumed" at a number of locations in a given model, for which Bus Duplicators are used.

Note

• Signal buses are strictly unidirectional. Data flows from the creator to the selector, and never in the opposite (or "upstream") direction. Additionally, it must be noted that the Bus Creator component for a given bus is the only place where signals can be inserted into that specific bus. This is in contradiction with legacy buses, which allow users to add signals to a bus anywhere in the bus's path, and thus expose users to signals that could hold several values, which differ depending on the location where they are extracted.

• It is possible to add signals to an existing bus (i.e. downstream of the bus creator component from which it originates), but only by nesting them into an additional bus, which would then contain both the original bus and the new signals that need to be added.

Figure 404: A simple circuit containing a signal bus

All of the above-mentioned features are available in the signal bus menu:

Figure 405: The signal bus menu

You can connect Bus creators to Bus selectors with lines in the same way as with other components.

Note

Signal buses are specific objects, and are therefore incompatible with the rest of the Signal, Control library. Inputs into a creator component are of the signal type (but can also be of the bus type in the case of nested buses). Likewise, outputs from a selector component are of the signal type. On the other hand, connections between bus components are of the bus type, i.e. the ports which are being connected (typically outputs of bus creators, inputs of bus selectors, and all ports of bus duplicators) are of the specific type bus, rendering them incompatible with components of the Signal, Control library.

Figure 406: Connecting bus components

The Bus Creator in detail

By default, dropping a Bus Creator component on the sketch creates a component which takes two inputs, and outputs a bus type signal. To adjust the number of inputs that the Bus Creator takes, the user must click the component. This automatically changes the Sketch contextual toolbar, displaying a button labeled Edit bus.

Figure 407: Editing a signal bus creator

Clicking on this button brings up a dialog window where it is possible to simultaneously modify the number of inputs to the creator and adjust their individual text identifiers.

Note

All characters are supported in bus signal Input names, except for the period (.).

Figure 408: Adjusting the number of inputs and identifiers for a bus creator component

Note

• Once a Bus creator is connected to other signal bus components, all of the information related to its contents is propagated towards those components. This information includes the structure of the bus (whether it is flat or contains nested buses), the number of signals, and their associated text identifiers. Information propagation holds true for signal bus components which reside within supercomponents; the information is made available regardless of the depth at which the signal bus components are located.

• It is also possible to edit a signal bus by right-clicking the bus component and choosing the "Edit bus" contextual menu item: Figure 409: Editing a signal bus using the contextual menu