Does the RC branch connected to the output as shown serve as a low pass filter? Shouldn't the output be tapped after the 50 Ohm resistor if it were to be used as a filter?
Electronic – the purpose of RC in series on FPGA output pin
filterfpgaio
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Best Answer
If the resistor value was anything other than either 50 ohm, 75 ohm, 100 ohm or 120 ohm I might give the answer that it was for general deglitching of an IO line.
So, it's probably a 50 ohm data termination that doesn't screw up the DC levels of the data signals (because of the 1200 pF capacitor) but does significantly cut-down on the transmission-line reflections. I've also seen as 51 ohm in series with 100 pF (and I've used similar to fix some rogue RS485 problems): -
Picture taken from Here.