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Altera_Forum's avatar
Altera_Forum
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14 years ago

Hyperlynx IBIS : What is cmos25_io_r50

Hi everyone,

I'm currently performing Hyperlynx simulations of an Arria II Gx FPGA design. I generated my ibis model with Quartus 11.0sp1 So far, everything works pretty good however I have some questions :

Some of my outputs have this model "cmos25_io_r50"

Basically a 2.5V output (which is what I specified) with a 50-ohm impedance? Where does the 50-ohm come from?

I also have other 2.5 outputs like this one "cmos25_io_d4", which mean a 2.5V LVCMOS drive with 4 mA of strength.

Thanks

4 Replies

  • Altera_Forum's avatar
    Altera_Forum
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    11 years ago

    Hello Benjamin_Couillard,

    I am pretty sure you would have sorted this out by now.

    however just for the benefit of future readers / users who might stumble across this thread.

    if you do not explicitly set a current strength for your I/O standard, i.e. you do not change the default I/O Standard in Pin Planner, then the current strength will be set to the default settings for the device.

    https://www.altera.com/support/support-resources/knowledge-base/solutions/rd08292012_329.html

    So for your case, since i assume you left the I/O standard / current strength settings as the default values in Quartus, that is why you see the 50-ohm series termination without calibration in your generated IBIS model =)

    You can double check this in your Fitter Report.

    just giving you 2 scenarios to help explain the differences a little more clearly.

    scenario# 1

    setup in pin planner

    - I/O Standard = 2.5 V (default)

    - Current Strength = 12mA (default)

    fitter report

    name

    pin#

    i/o bank

    i/o standard

    current strength

    termination

    led0

    AK3

    3B

    2.5 V

    Default

    Series 50 Ohm without Calibration

    scenario# 2

    setup in pin planner

    - I/O Standard = 2.5 V

    - Current Strength = 12mA

    fitter report

    name

    pin#

    i/o bank

    i/o standard

    current strength

    termination

    led0

    AK3

    3B

    2.5 V

    12mA

    Off

    thanx.
  • Altera_Forum's avatar
    Altera_Forum
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    11 years ago

    Hi,

    You could find the naming nomenclature of the Arria II GX IBIS model in the Notes section of the .ibs file. Specific to the r50 and d4, you can refer to the following text extracted from the .ibs file:

    d12 - 12mA Current Strength

    r25 - 25 Ohm series on-chip Termination without Calibration

    r50c - 50 Ohm series on-chip Termination with Calibration

    r50 (without the 'c') mean 50 Ohm series on-chip Termination without Calibration
  • Altera_Forum's avatar
    Altera_Forum
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    11 years ago

    By the way, I believe when you download the Arria II GX IBIS model zip from the Altera web, there is a document called ArriaIIGX_IBIS_Model_User_Guide.pdf together inside the zip. There is explanation on the Naming Nomenclature as well in this doc.