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signal from input pin to output pin inverted

PhilipJ451
Beginner
341 Views

I am designing with Quartus Prime v19.1.0 for a Cyclone 10 device.

I have two clock inputs into the design and for convenience I feed these signals to output pins with test points connected (along with other signals for design analysis).

Dante_SCLK: in std_logic;
Dante_LRCK: in std_logic;

TP3: out std_logic;
TP5: out std_logic;

TP3 <= Dante_SCLK;
TP5 <= Dante_LRCK;

When examined with an oscilloscope, the signal 'Dante_SCLK' is inverted!!

This is highly misleading and results in confusion, mistakes and time wasted trying to debug why the design appears to be wrong.

 

Can anyone explain why this happens and what I need to do to stop it.

PhilipJ

 

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1 Reply
PhilipJ451
Beginner
334 Views

Sorry All, ignore this!!

Confusion with another part of the system (not FPGA) generating the signal the wrong way up, and me getting confused on the oscilloscope between 1/2 the period of the clock (~20nS) and the natural delay through the FPGA from input pin to output pin

regards

PhilipJ

 

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