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PAA's avatar
PAA
Icon for New Contributor rankNew Contributor
1 year ago

Enabling OCT termination for Agilex5 Differential bi-drectional IOs

Hi,

I am attempting to enable OCT termination for a bidirectional differential IOs for Agilex5.

Due to the bidirectional nature, I can use only 'Differential 1.2v POD' or 'Differential 1.2v SSTL'.
By default, these signals have dynamic OCT enabled, which is active when the data is received, and switched off (no termination), when the signals are outputting data.
Both of these signals operate with a full swing of 1.2V with the n signal inverted to the p. Thus the differential output is seen to be 2.4V, which makes it out of specifications for the received.
As a work around I am trying to activate the Output OCT termination on these signals, but it seems to be failing.
When I set the out put termination to simply 'parallel' the error message states that the termination is being set to 'off' and not acceptable for the differential signal standard of the receiver.
When I set to 'Differential' or 'parallel termination 50 ohm' (calibrated or uncalibrated) , I get the message 'setting is not supported by I/O standard'

For example:
Error(12418): Termination logic option is set to Differential for input pin tx_aux_diff_io|gpio_0|core|i_loop[0].altera_gpio_bit_i|input_buffer.ibuf, but setting is not supported by I/O standard Differential 1.2-V POD

Could someone clarify if I can set any / all of the following :
1. Either disable 'dynamic' OCT termination for differential 1.2V SSTL or differential 1.2V POD to use external termination.

2.Enable OCT for input as we as output for differential SSTL IO
3.Enable OCT for input as we as output for differential POD IO

The Altera document 813934 | 2024.04.05 (ug-813934-813935.pdf) does not clarify if Rt can or cannot be used when differential signals are in output mode.

Generic Io

5 Replies

  • PAA's avatar
    PAA
    Icon for New Contributor rankNew Contributor
    1 year ago

    Settings mentioned in my message are being applied in the Assignment editor itself!

    I am unable to disable the disable the OCT to use external termination. The settings seems to be applied correctly, but when we observer the signals on the oscilloscope, the Rx diff voltage is seen to be half of Tx, implying that the OCT is being switched on and off dynamically.

  • AqidAyman_Altera's avatar
    AqidAyman_Altera
    Icon for Regular Contributor rankRegular Contributor
    1 year ago

    Thank you for the clarification. Can you help to share the example designs that demonstrate this issue?


    It will help me to replicate so that I can investigate further this issue.


  • AqidAyman_Altera's avatar
    AqidAyman_Altera
    Icon for Regular Contributor rankRegular Contributor
    1 year ago

    Hello,


    I wish to follow up with you.

    Do you have any updates on the requested design file?


  • AqidAyman_Altera's avatar
    AqidAyman_Altera
    Icon for Regular Contributor rankRegular Contributor
    1 year ago

    As we do not receive any response from you on the previous question/reply/answer that we have provided. Please login to ‘https://supporttickets.intel.com/s/?language=en_US’, view details of the desire request, and post a feed/response within the next 15 days to allow me to continue to support you. After 15 days, this thread will be transitioned to community support. The community users will be able to help you on your follow-up questions.