Bus-based Systems
Use the following links to browse through the frequently asked questions relevant to this area of soft design.
- Can I use the new signal harness features in FPGA design projects created before the Winter 09 release of Altium Designer?
- What if I don't want to use signal harnesses in my FPGA design project?
- Harness entries do not have directions, so where can I find the directions of the pins exported from OpenBus components?
- Why is the synchronize ports to sheet entries tool not updating the harness type of the sheet entry?
- How does the OpenBus Dual Port Connector component work?
Can I use the new signal harness features in FPGA design projects created before the Winter 09 release of Altium Designer?
OpenBus System documents created prior to the Winter 09 release of Altium Designer do not support the signal harness feature. For such documents, a pin interface will always be exported to higher level sheets. The OpenBus components in these older documents will need to be replaced with new ones from the OpenBus Palette panel.
What if I don't want to use signal harnesses in my FPGA design project?
By default, OpenBus components are set to export external interface signals as a signal harness-type interface. However you can, should you wish, specify that the individual pins for the interface be exported instead. This was the behavior in releases of Altium Designer prior to Winter 09.
If an OpenBus component should export a pin interface, double click on the component to access its configuration dialog. Then simply change the Interface Type option to Pins. This property can also be edited via the OpenBus Inspector panel.
Changing the Interface Type for an OpenBus component.
Harness entries do not have directions, so where can I find the directions of the pins exported from OpenBus components?
The directions of the pins connected to harness entries can be viewed on the External connection summary tab of the OpenBus Signal Manager dialog (Tools » OpenBus Signal Manager). This tab shows the interface which is exported for each OpenBus component and the directions of the component's pins.
The OpenBus Signal Manager dialog is also accessible by pressing the Manage Signals button, located at the bottom-left corner of the configuration dialog for an OpenBus component.
Use the OpenBus Signal Manager dialog to view the directions of pins for OpenBus components.
Why is the synchronize ports to sheet entries tool not updating the harness type of the sheet entry?
When a sheet entry or port is connected to a harness connector, it will automatically be forced to assume the harness type of the connector. The harness type of the sheet entry cannot be edited in the Sheet Entry Properties dialog. Therefore, when replacing an existing sheet entry during synchronization, ensure that the sheet entry is not connected to any harness connectors.
How does the OpenBus Dual Port Connector component work?
The Dual Port Connector essentially breaks the OpenBus link within which it is placed. Both sides of the link (master and slave) are exposed at the schematic level. In order to keep continuity of the link within the OpenBus System document, you must ensure that the bus is routed back into the system. This is achieved most simply by looping the output signals back to the input signals for the bus.
Example exposure of bus signals for analysis using a Logic Analyzer instrument.