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Altera_Forum
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10 years ago

OCT Termination - how many pins?

Hello

I want to use 50 ohm oct termination with calibration on an Cyclone IV E device (EP4CE55F23C7).

In the QSF file i define the termination for a 8bit bus RAM0_DQA:

set_instance_assignment -name OUTPUT_TERMINATION "SERIES 50 OHM WITH CALIBRATION" -to RAM0_DQA

That seems to work - I get no error from Quratus 15.1

But as I have a 128 bit data interface to an 250MHz SRAM, I have to make the above assignment to all the data pins. Now it seems quartus only can place about 80 pins with OCT termination.

With more pins I get the following Error:

Error (176210): Can't place pin RAM2_DQB[1] with I/O standard 2.5 V, Termination setting Off, and PCI I/O setting on due to device constraints

What´s the reason for that?

If I assign no oct termination, the design dose fit.

How many pins can use the oct feature?

Best Regards

Robert

3 Replies

  • Altera_Forum's avatar
    Altera_Forum
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    10 years ago

    --- Quote Start ---

    Hello

    With more pins I get the following Error:

    Error (176210): Can't place pin RAM2_DQB[1] with I/O standard 2.5 V, Termination setting Off, and PCI I/O setting on due to device constraints

    --- Quote End ---

    Hi Robert, are pin on supported side/bank?

    From user manual cyiv-51006.pdf you can find here https://www.altera.com/products/fpga/cyclone-series/cyclone-iv/features.html

    bottom of page right column "connectivity" line I/O Features (pdf)

    at page 8 we read:

    cyclone iv devices support r s oct with calibration in the top, bottom, and right i/o

    banks. the r s oct calibration circuit compares the total impedance of the i/o buffer

    to the external 25 ohm ±1% or 50 ohm ±1% resistors connected to the rup and rdn pins, and

    dynamically adjusts the i/o buffer impedance until they match (as shown in

    figure 6–2).

    --- Quote Start ---

    Error (176210): Can't place pin RAM2_DQB[1] with I/O standard 2.5 V, Termination setting Off, and PCI I/O setting on due to device constraints

    What´s the reason for that?

    If I assign no oct termination, the design dose fit.

    How many pins can use the oct feature?

    --- Quote End ---

    http://quartushelp.altera.com/14.0/mergedprojects/msgs/msgs.htm

    insert your error number, the error appear under the search pane then click on it and read the help about constraint.

    Or faster from quartus click on error to go to this help page.

    If this doesn't help please post pin assignment.

    Best regards
  • Altera_Forum's avatar
    Altera_Forum
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    10 years ago

    Hello rromano001

    Thanks for your answer. I´ve solved the problem in meantime.

    Tho one thing is do assign the output termination to a number of pins. The pins also have to be assigned to a bank. As far as there are enough pins in that bank, it works. Without a termination quartus fitter spreads the pins to several banks and everything is fine. With a termination quartus fitter dose not spread the pins, and user has to do that.

    Best Regards
  • Altera_Forum's avatar
    Altera_Forum
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    10 years ago

    Good to read that, to be of help to other a question,

    Is Quartus spreading in bank where no OCT is active

    or

    when a Calibration are assigned to pin lock something to?

    Thank for sharing solution.

    Roberto