Can I use 50 Ohm calibrated bidirectional pins on an Arria 10 - seems not?

[RPDM]

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...

[YuanLi_S_Intel]

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

[RPDM]

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

[YuanLi_S_Intel]

Hi Richard,

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

Thank You.

Regards,

Yuan Li

[RPDM]

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

[YuanLi_S_Intel]

​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

[RPDM]

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

[YuanLi_S_Intel · Accepted solution]

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