Synthesis

[xx77abs]

Can anyone explain to me how can I disable XST FF/Latch trimming ? In this particular example, I know why trimmings are occurring (I don't want to go into details), but they are occurring on very large std_logic_vector (two vectors with 128 bits).

That said, I get many warnings and can't see if anything else is wrong (that I would care about). So I would like to hide warnings or disable FF/Latch trimming. Is that possible ?

Thanks !

[gszakacs · Accepted solution]

In the ISE GUI you can enable "message filtering" and then using the "Design Summary" view,

select "Synthesis Messages" to see the warnings, infos, errors, etc.  Then right-click the message

about trimming and select "hide all instances of this message."  If there are other warnings that

you don't want to miss, like un-driven nets, then you can use the same procedures to "Highlight

all instances of this message," which makes them stand out in red.

If you don't want the nets trimmed, you can place a "KEEP" attribute on the nets (see the XST

user guide for details on how to apply this constraint), or in the synthesis properties you can

disable the check box for "equivalent register removal."  The latter usually helps when you

have a large word that has a number of bits that always track each other.  It won't help with

bits that are always high or always low.

HTH,

Gabor

[xx77abs]

Thank you !!

I've tried both KEEP attribute and message filtering and decided to go with message filtering because I want these nets to be trimmed, just don't want to see hundreds of warnings :) This is perfect, thank you !