A bus is an open shape that represents a collection of signals on the schematic design. This makes the schematic less cluttered as you do not need lots of parallel connections running from one side of the drawing to the other. Simply add a connection from a pin to the bus that carries the required signal.
Shortcuts
Default Keys: None
Default Menu: Insert
Command: Insert Bus
Locating this option
Available from: Insert menu > Insert Bus option
More about Busses
Open and Closed Busses
A newly added bus is open to carry any net names. You can close it to only carry a closed set of names by selecting it and using Properties from the Edit menu. If you already have a closed bus in the design, you can use the Change Bus option from the context menu to make a new bus the same type as an existing one.
Once closed, you can only add a connection to the bus if the connection is on one of the nets defined in the bus’s set of net names. When trying to connect to a closed bus, you will be presented with a list of the bus’s net names to choose from.
The set of allowed net names can be displayed next to the bus using a condensed range format. Select the bus and right click to use Show Net Name from the shortcut menu. Then drag the name range to the desired position.
Naming Busses
A closed bus can be allocated a name using the Properties dialog. All closed busses with the same name are forced to always contain the same set of allowed net names. This name can used in the Find and Change Bus operations and can be displayed next to the bus.
Joining Busses
Two busses can be joined together by adding segments at the end of one and finishing anywhere on the other, or by starting a new bus on the segment of an existing one. They are joined with an invisible junction and will stay attached during further interaction. Once busses are joined they will always have the same bus name and sets of net names. To join them in the first place they must be compatible as follows:
- If both are named they must have the same name.
- If any are open busses, they must not have connections attached.
- If only one is named, the other must have a set of net names that are a subset of the nets on the named bus.
If two unnamed closed busses are joined with incompatible net names, you will be warned and they will both end up with the same superset of the net names.
Bus Terminals
When a connection is attached to a bus segment, the end of the connection is bent at 45 degrees as it touches the bus. This 45 degree segment is known as a Bus Terminal. It takes it’s colour and width from the connection, but it is not part of the connection.
To alter it’s length, select it and use Properties from the Edit menu. To set the default length they are added with, from the Setup menu use the Bus Defaults dialog and change the bus offset to the required value.
The bus terminal may not be initially added in the preferred direction, to alter this select it and use the Rotate option to flip between the allowed angles.
When the connection segment attached to the bus terminal is moved, the bus terminal moves with it to the nearest place on the bus. When the bus segment is moved all bus terminals attached to it are moved with it to keep the bus together.
The net name can be displayed next to the bus terminal. Select the bus terminal and right click to use Show Net Name from the shortcut menu. Then drag the name to the desired position. Use Options - Edit Connection tab to enable automatic display of net name when connecting to a bus.
When a connection to a bus is deleted, the bus terminal is also deleted.
Translate To PCB
When the schematic is transferred to a PCB design, each bus is split up into the different connections that use it.
Connecting from a Bus to a Bus on another page
You can end a bus on a Bus Reference symbol, and you can add the
Special Considerations - Bus Pins - Connections from a Bus to a Block Port
When creating a bus in your Schematic design, if also using Hierarchy, you can directly connect a set of nets defined in a closed bus into the hierarchical block using a method called Bus Pins. In Pulsonix this is a simple process where you can connect the end of the bus during a bus edit, to a Block Port of the hierarchical block. If you move the mouse over the Block Port, the Finish marker will be displayed indicating it can be connected to. Once you navigate to the lower level block, the matching block port will now contain all the nets defined in that bus. If you connect a bus to that lower level pin, it will now carry all the net names from above.
How To Insert A Bus
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Before entering Insert Bus, optionally select an existing bus if you want to create a bus with the same name, line width and allowed nets.
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On the Schematics Edit Toolbar select the Insert Bus Icon.
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From the Insert menu select Bus.
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Right click to use the shortcut menu to use Change Style to change the bus width, Change Bus to change the bus type to match an existing closed bus, or Start Connection On to insert an item to start the connection from.
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Left click to pick the start position. You can also start the bus on another bus segment to create attached busses representing the same signals, or you can start it from a block terminal or port to take the bus down through a hierarchical design.
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Left click to add each corner in turn.
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Double click the left mouse button to finish. If Start Connection On was used, the moving start item will be dropped at the picked location and the new connection will start from it’s pin. See the procedure for Edit Bus for a more detailed description of the procedure to add bus segments.
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If required use Properties, as mentioned above, to add allowed net names to the bus, and optionally give the bus a name.
Related Topics
Change Bus Type | Change Style | Edit Bus | Properties - Bus | Properties - Bus Terminal | Bus Defaults | Options - Edit Connection | Rotate