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set_max_delay / set_min_delay & set_output_delay query


I tried constraining the following using set_max_delay & set_min_delay  flash_nce output port :

set PERIOD_CLK 100.000

create_clock -name {clk} -period $PERIOD_CLK -waveform { 0.000 50.000 } [get_ports {in_clk}]

create_clock -name {clk_virt} -period $PERIOD_CLK -waveform { 0.000 50.000 }

set_max_delay -from [get_ports {in_clk}] -to [get_ports flash_nce] 70

set_min_delay -from [get_ports {in_clk}] -to [get_ports flash_nce] 50


Note: Suggestion in one of the PFL documents was to constrain eg flash_nce using set_max_delay.  Had to also add set_min_delay  constraint because it was reported as partially constrained.

However, STA (Static Timing Analyzer) tool still reported 'unconstrained output port within unconstrained paths/summary section.

Had to add the following too to resolve the 'no output constraint on flash_nce' : 

set output_max 70.0
set output_min 50.0

set_output_delay -clock clk_virt \
-max $output_max \
[get_ports flash_nce]

set_output_delay -clock clk_virt \
-min $output_min \
[get_ports flash_nce]



Same with the following constraint :

create_generated_clock -name dclk1 -source [get_ports in_clk] -divide_by 1 -invert [get_ports fpga_dclk]


It still reported 'No output delay was set on output fpga_dclk port. This port has clock assignments'

Can I ignore this warning ?


Please comment here.

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1 Reply

Hi Kevin,

Can you try to add set_output_delay constraint to fpga_dclk port and see if there is warning regarding it.