In the vector waveform file that I am creating to enter the inputs for my simulation I can also enter the outputs and the registers that I would like to be recorded. There using the node finder I can enter some combinatorial signals that I would like to observe. But after the simulation those signals have been omitted and the warning has been given : "Warning: Ignored node in vector source file. Can't find corresponding node name CFCstatus in design."
So, can someone please explain me how I can check those internal signals? For example the output of a lpm_compare block which feeds an input of a counter without inserting in the middle a output pin? (you don't have to use this example of course).
I thing it doesn't make any difference the version but I am using Quartus II
To preserve a combinatorial node through synthesis, place and route, you should do one of the following:
a) If it is a BDF (schematic file) or TDF (AHDL file), feed the signal that you are interested in observing into a LCELL primitive, and give the LCELL primitive an interesting name, so that you can find it when you choose the Post Compilation filter in the node finder. You should feed the output of the LCELL to where the signal wof interes was previously connected.
b) If you are using VHDL or Verilog, consider using the keep pragma/keyword. Its usage is described in the online help. Search for "keep". The Verilog help panel is shown below:
------------------- keep usage in Verilog
----------------------------------- A Verilog HDL language directive that directs Analysis & Synthesis to keep a particular wire intact. You can use this language directive to keep a combinational logic node so you can observe the node during simulation or with the SignalTap® II Logic Analyzer.
You cannot use this language directive for nodes that have no fan-out.
To use the keep language directive, you can specify the keep language directive in a comment that is on the same line as the register you want Analysis & Synthesis to preserve. In the comment, precede the language directive with the synthesis keyword.
For example, in the following code, the comment /* synthesis preserve
*/ directs Analysis & Synthesis to not minimize the keep_wire register:
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