about EPM240 high impedance output

just to understand you a bit more

So the green line is A and the violett line is B

during adjlevel = 1 A is max 3,3V as this is the EPMs IO voltage and B is 0V

A can't reach 5V as the pull up won't be feed with 5V

during adjlevel = 0 A and B are around 2V +/- something

so you would expect A and B going from 0V to 3,3V what is not the case and you assume 1'bz not working

and the blue signal shows a correct waveform ?

80nsec = 12,5MHz ? that clock should be seen between A and B during 1'bz

wont't you need some termination resistor between A and B ? like 150Ohm or something matching to your cable ?

What about the other side of the RS485 can it drive a 12,5MHz clock ?