CYCLONE V OCT Problem

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The Cyclone V devices provide a 100 Ω, on-chip differential termination option on each differential receiver channel for LVDS standards. On-chip termination saves board space by eliminating the need to add external resistors on the board. You can enable on-chip termination in the Quartus Prime software Assignment Editor.

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By selecting LVDS you will automatically get the termination resistor. However, you can remove this by setting the 'Input Termination' to 'Off', or adding a line to the project's Quartus Settings File (.qsf):

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set_instance_assignment -name INPUT_TERMINATION OFF -to your_input_signal

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Cheers,

Alex

Hi Alex,

Thank you for your reply.

So, I receive differential termination by default, can I alter this value to a new value of my choosing?

Also, currently in my design the RZQ resistor is not connected.

From Altera's handbook I can see this resistor is used for calibration purposes, what is the termination value if this resistor is missing?

Thanks,

Refael.

You can adjust the On-Chip Termination (OCT) via this same 'Input Termination' parameter - various OCT options are available. However, I'm sure not all (if any) of the the OCT options will be valid for LVDS. I suspect you'll only be able to switch it OFF or leave it a it's default. Play around with it to see.

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what is the termination value if this resistor is missing?

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Something that's not correct. The handbook doesn't cover this eventuality. Unfortunately, if you've not followed the guidelines, you're on your own. However,

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Some specific DQ pins can also be used as RZQ pins. If you need extra RZQ pins, you can use these [the] DQ pins as RZQ pins instead.

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So, depending on your board you may be able to salvage something by using an alternative pin.

Cheers,

Alex