can't find 'clk' pin using get_pins in timequest timing analyzer

Question

using quartus 11.1 build 216 w/service pack 1. My design uses LPM_ADD_SUB components, with the results output registered (not the pipeline registers in the component). I am trying to do report_path in timequest timing analyzer, to see the delay from my clock pin to one of the registers that is at the output of the LPM_ADD_SUB's 'result' output pin. However, when I try to find the 'clk' pin using the name finder, I can't see the 'clk' pins - only the datapath pins to the LE associated with the register. In chip planner, I can clearly see the registers, so I know they are there and not optimized away.

has anyone else had this problem? any solutions?

altera_forum · Answer

Something llike get_pins *|clk works for me..

altera_forum · Answer

yes, I tried that - doesn't find the pins I'm looking for.  it's a tool problem or an optimization problem.  I was hoping that someone else had a similar problem and found a workaround.

altera_forum · Answer

I have the same problem but with Version 9.1SP2. (I have to use this rather old version, since recent versions don't accept my pci licenze file).

I want to specify a generated_clock timing constraint.

With:

get_registers {*|registername}

I get the register i want.

But if I use

get_pins {*|registername|clk}

I get the warning that the filter coudn't be matched.

Any ideas?

altera_forum · Answer

Well, my situation turned out to be a register that wasn't driving anything. In the process of creating my design, I had registers that were not driving any logic or outputs. I think this is a bug in the timing analyzer.

If this is your situation, either send the output of the register to a pin on your device, or create a virtual output and drive that.

altera_forum · Answer

Thanks for your reply.

I once had the same problem as you. (registers driving no logic)

I solved this by using the synthessis attribute noprune.

signal registerIwantToKeep : std_logic;

attribute keep : boolean;

attribute keep registerIwantToKeep : signal is true;

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can't find 'clk' pin using get_pins in timequest timing analyzer

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