Hi everybody,
After synthesizing my architecture using Synplify pro, i received several same warning like:
... hdl\FSM_Write.vhd":65:7:65:8|Pruning Register ......
what does it mean Pruning register? i noticed that it doesn t affect the behviour of my architecture. I found in one forum that it means that the register was removed, is it true???? i don t think so, because i need that register in my architecture.
Thank you for your help! A.
Yes, "pruning register" means that it is removing a register from the design. Think of the synthesis tool as a diligent gardener, carefully removing stray branches from the mildly overgrown shrub that is your design.
Reasons it might do this are:
(1) The register doesn't drive any other logic, and so is unnecessary (2) The register is a duplicate of another register and only one is needed (3) The regsiter's value can be shown never to change during operation (4) ...maybe some other reasons I forgot about.
The synthesis tool is "guaranteed" not to break the functional correctness of your circuit when pruning registers. That is, if you simulate what comes out of Synplify, you'll find it does the exact same thing that your original code did. If it *doesn't*, then you have found a bug in Synplify and you'll need to complain to Synplicity about it. That's pretty unlikely though.
Cheers,
-Ben-
Hi Ben!
Thank you for these information, and specially for that sentence: "The synthesis tool is "guaranteed" not to break the functional correctness of your circuit when pruning registers", that's what i wanted to know.
Thank you, A.
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