Can I use 50 Ohm calibrated bidirectional pins on an Arria 10 - seems not? - Can I use 50 Ohm calibrated bidirectional pins on an Arria 10 - seems not? So I've replicated this on two different Arria 10 devices (10AX027 & 10AS066) and if I create a bidirectional pin I cannot get it to output something if set to a 50 Ohm calibrated output. So: set to 1.8v 50 Ohm uncalibrated , it outputs the expected signal (when the output enable I send to the pin is high, of course). But: just change uncalibrated to calibrated (with a reference 100 Ohm RZQ pin), and there's no output - just a signal at GND. Changing the bidirectional ability to just being an output pin, still 50 Ohm calibrated, works fine. The Handbook appears to show what I'm doing is valid - but it doesn't work... Replies: Re: Can I use 50 Ohm calibrated bidirectional pins on an Arria 10 - seems not? Hi RPDM, It is hardware restriction that bidirectional cannot have OCT for GPIO. However, when the I/O pin is used with external memory interface IP, bidirectional with OCT is allowed. Regards, YL Replies: Re: Can I use 50 Ohm calibrated bidirectional pins on an Arria 10 - seems not? Hi Yuan, My last test was using 18.1. I've not tried since. This is obviously an issue for us. Will it be fixed in a newer version of Quartus, or is it a hardware issue? I am assuming that it does not affect Intel's External Memory Interface IP, since that obviously needs calibrated bi-directional pins? Regards, Richard Replies: Re: Can I use 50 Ohm calibrated bidirectional pins on an Arria 10 - seems not? Hi Richard, May I know which quartus version you are using? I have checked with internal team, OCT cannot be enabled for bidirectional pin. Regards, YL Replies: Re: Can I use 50 Ohm calibrated bidirectional pins on an Arria 10 - seems not? Hi Yuan, I have checked 4 different pins on a 10AX027H4F35E3SG device, plus 1 pin on the 10AS066 that's on the SoC dev board. All behave in the same way. Some tests I've done: Pin = inout, GPIO IP = Bidirectional, Calibration = On, Result = No output Pin = inout, GPIO IP = Bidirectional, Calibration = Off, Result = OK Pin = inout, GPIO IP = Output with OE (variable), Calibration = On, Result = No output Pin = inout, GPIO IP = Output with OE (fixed to '1'), Calibration = On, Result = No output Pin = inout, Simple Verilog code with OE (Variable), Calibration = On, Result = No output Pin = inout, Simple Verilog code with OE (Variable), Calibration = Off, Result = OK Pin = output, GPIO IP = Output with OE (variable), Calibration = On, Result = OK Resource Property Viewer shows the correct connections in all cases. It also shows Open Drain = Off. The "Simple Verilog code with OE" was just this (showing just the appropriate lines of code): inout m1_c1_dq10, ... assign m1_c1_dq10 = counter[2] ? counter[0] : 1'bZ; With the above, calibrated outputs fail, non-calibrated ones work. RPV shows the correct connections (with Open Drain=Off). Regards, Richard Replies: Re: Can I use 50 Ohm calibrated bidirectional pins on an Arria 10 - seems not? Hi Richard, This is abnormal, by right it should work. Can you check on the other pin? Thank You. Regards, Yuan Li Replies: Re: Can I use 50 Ohm calibrated bidirectional pins on an Arria 10 - seems not? Hi, Yes, that's correct. When set to uncalibrated, the bidirectional pin works correctly. When set to calibrated, the bidirectional pin does not output anything. Thanks, Richard Replies: Re: Can I use 50 Ohm calibrated bidirectional pins on an Arria 10 - seems not? Hi RPDM, Apologize that I don’t understand the enquiry. Are you saying that the bidirectional pin in Arria 10, there is no problem in using 50 Ohm uncalibrated On-chip termination (OCT) but there is problem in using 50 Ohm calibrated OCT? Regards, YL