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Pie566942.0

Enumerate the Top Level Clock in the FPGA Clock Control

Status: New

In LabVIEW FPGA 2011, only the base clocks enumerated in the project and clocks derived from the base clock(s) are available in the FPGA Clock Control. I’d like LabVIEW to show the top level clock in this control as well.

 

Consider designs with nested components that both CAN and CANNOT be optimized with the single-cycle timed loop. If the domain of the SCTL does not match the top-level clock domain that contains it, you seem to pay a heavy performance penalty. I presume it’s due to the clock-crossing logic under the hood. Thank you, by the way, for dealing with this for me!  For example, consider this VI:

 

2013-03-04_164826.png

 

The While Loop will take more ticks (a few hundred more in cases I’ve seen) to execute than if the Clock Control constant was set to 200MHz (assuming you could compile). So, just set the TLC and the clock control to be the same, right? Sure, except when you change the top-level clock and a few hours later, when the compile is finished, realized you forgot (gasp) to change a clock constant and the code doesn't fill its timing requirement anymore.

 

Project Clocks:

2013-03-04_163653.png

 

LabVIEW 2011 Behavior:

2013-03-04_163818.png

 

Desired Behavior:

2013-03-04_163818b.png

 

Thanks!

 

-Steve K