Manually routing allows you to fine tune your design or improve PAR's performance. You can use FPGA Editor to manually route your design for Design Implementation as follows.
Run place and route on your design.
After you run Place and Route, double-click on View/Edit Routed Design (FPGA Editor) process to open FPGA Editor.
Click the left mouse button to select the source pin wire.
Press the Ctrl key and the left mouse button simultaneously to select additional routing resources.
You must select objects in the order in which you want them routed. When you select the objects, consider that connections are routed one by one from each selected object to the next. For example, if you select three objects in the order A, B, C, you are indicating that you want to route A to B, then route B to C.
Select Tools > Route > Manual Route.
The selected objects are routed in the specified order.
To exit FPGA Editor, select File > Exit.
Selected objects must be part of the same net. For example, you cannot select a net pin that is part of one net and a long line that is part of another net.
When a connection does not exist between specified objects, that connection is not routed and an error message appears in the History toolbar. By default, FPGA Editor attempts to autoroute between the two selected routing resources. This option can be disabled.
When you specify objects to route, consider the direction of current flow through the switches connecting the two objects. You can route from source to load or from load to source, but you cannot mix the two directions during a single Route command run.
When you select an unused net pin or pinwire for a connection, it is added to the net you are routing.
Manual routing only routes the specified connections. All other unrouted connections on the applicable net remain unrouted, unless the Enhanced Manual Routing option is enabled in the Main Properties property sheet.
The Stub Trimming option displays only those portions of routing resources, for example, long lines and local lines, actually used by routes. If you disable Stub Trimming, the full routing resources taken up by the routes are displayed. For manual routing, disable Stub Trimming to determine which routing resources are available.
Partially routed nets that do not terminate at pins (antennas) are unrouted by the Autoroute -all command if you do not lock the net. Unlocked antennas are also removed if you run PAR on your design file.
Any segment added to a net with manual routing is locked or unlocked, depending on the net's lock status.
You may want to specify Automatic Hilite if you are manually routing a very dense design.
You must select objects in the order in which you want them routed. When you select the objects, connections can be routed one by one from each selected object to the next or in a " fanout" pattern. For example, if you select three objects in the order A, B, C, you are indicating that you want to route A to B, then route B to C. If you use the - fanout option, you can route A to B and A to C.
After working in FPGA Editor, you will have a modified NCD and PCF file.
Analyze design through timing constraints in Timing Analyzer.
See Also
Cross
Probing with Timing Analyzer
Verifying Your Design