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Altera_Forum's avatar
Altera_Forum
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10 years ago

set_max_skew command

I'm clocking a data bus out of my Cyclone V and want to constrain the maximum skew between data lines. I'm using; # 100 ps max skew set_max_skew -to [get_ports data_out [*]] 0.1 It seem...
Altera_Forum's avatar
Altera_Forum
Icon for Honored Contributor rankHonored Contributor
10 years ago

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OK, agreed. But if I set my constraint to a value that (I think) can't possibly pass timing, for example;

set_max_skew -to [get_ports data_out

[*]] 0.0

Then wouldn't I expect TQ to report a failure?

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It depends on your io constraints i.e set_output_delay figures and clock rate.

skew does not tell TQ what are your actual constraints (clock data offset).

I know skew method is used for some cases of DDR if the external chip asks for skew only but I am not sure then how TQ check the tSU/tH. I believe in such cases the external chip doesn't care about data/clock offset as it may have automated logic to align.