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

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

Hi Richard,

This is abnormal, by right it should work. Can you check on the other pin?

Thank You.

Regards,

Yuan Li

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