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Altera_Forum
Honored Contributor
18 years agoderive_pll_clocks cmd and it's generated clk
Hi, I have a question regarding derive_pll_clocks. Quote taken from QII Handbook Vol 3 pg 6-36 Under title Derive PLL Clocks "If you use the write_sdc command after the derive_pll_clock ...
Altera_Forum
Honored Contributor
18 years agoIt probably used to write out the individual commands, but I believe write_sdc has been changed to try to look more like the original commands put into it rather than there "synthesized" versions. For example, if you did something like a wildcarded command like:
set_output_delay -clock outclock 4.0 dout* and dout* was a 32-bit bus, you'd end up with 128 individual dout commands, with -max/-min and -rise/-fall options, which was very annoying. That being said, you already have what you want. When you ran derive_pll_clocks and did derive_pll_clocks, there will be an info message in TimeQuest telling you the exact commands, so just cut and paste from there. I find that's useful, but I also recommend making use of the report_clocks command in the Task bar, which many people overlook but should have the same information(just not in SDC syntax, but it should have your input and output pin names you are looking for). Personally, I stay far away from write_sdc, and really haven't found any reason to use it. (It does write out a searchable text file, but I usually find what I want with report_sdc.)