CYCLONE V OCT Problem

[Altera_Forum]

Hi, 

 I am using in my design a Cyclone V device (namely the 5CGXBC3B7U15C8N), while using PIN#M13, N12 as an LVDS RX port. Going through ALTERA device handbook, it has two variations for On Chip Termination:  - Embedded inside FPGA.  - On board termination.  Does declaring LVDS inside QUARTUSII automatically attributes a 100ohm OCT for this pair?  Thank you for your answers, Refael.

[Altera_Forum]

--- Quote Start ---  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.  --- Quote End ---   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):    --- Quote Start ---  set_instance_assignment -name INPUT_TERMINATION OFF -to your_input_signal  --- Quote End ---   Cheers, Alex

[Altera_Forum]

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.

[Altera_Forum]

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. 

   --- Quote Start ---  what is the termination value if this resistor is missing?  --- Quote End ---  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,    --- Quote Start ---  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.  --- Quote End ---  So, depending on your board you may be able to salvage something by using an alternative pin.  Cheers, Alex