Thanks, Tristan. I found the problem, and of course it is both obvious and trivial -- in retrospect.
The problem is that the port-signal clk2x is defined in unisim DCM.vhd as a std_ulogic, but my test bench, which derived from the old oc_ddr project, connected this port to a signal tclock defined as std_logic. Apparently, the DCM definition changed some time during the last two years. to fix it, I simply changed tclock to std_ulogic. I did find this by brute-force simplification, so the effort was not wasted, but this is a very inefficient debugging technique. I will study the --trace-signals and --disp-time options. In retrospect, what is need is a way to ask GHDL "what are the inputs to signal X at time Y?" However, until I learn some more VHDL, my guess is that I will not really understand the answer. In this instance, (apparently) the input is some sort of underlying attribute of any signal defined as std_logic. For those adept at VHDL, a connection of a std_logic to a std_ulogic is probably as easy to understand as adding an integer to a float in C, but it is very subtle to a newcomer. On Mon, Nov 9, 2009 at 12:23 AM, Tristan Gingold <tging...@free.fr> wrote: > On Sun, Nov 08, 2009 at 08:54:31PM -0500, Dan Clemmensen wrote: >> I thought of that. In the origional code, the instantiation connects >> clk2x to a signal named tclock, which in turn is connected to clk_fb >> and to nothing else. Just in case, I broke the connection from tclock >> to clk_fb, so clk2x is in effect connected to nothing externally. My >> "project" is now stripped down to a single VHDL file named mytb.vhd, >> plus the copied and stripped version of DCM.vhd, but it still exhibits >> the problem. >> >> This leads back to the original question: how do I debug this? I don't >> know ADA or VHDL very well, but I do know the GCC tools and their >> internals. > > Hi, > > there are some debug options that may help you (--trace-signals, --disp-time). > You can also send me the simplified design and I can investigate. > > Tristan. > > _______________________________________________ > Ghdl-discuss mailing list > Ghdl-discuss@gna.org > https://mail.gna.org/listinfo/ghdl-discuss > _______________________________________________ Ghdl-discuss mailing list Ghdl-discuss@gna.org https://mail.gna.org/listinfo/ghdl-discuss
