LVDS I/O termination

[Altera_Forum]

Is an external 100Ohm resistor required at the input of an LVDS receiver I/O pair for the Cyclone III devices? The literature seems to suggest yes and no. Also, if I have "rx_in" as a single-channel LVDS serial input to my deserializer on the FPGA, is it correct to assume that "rx_in", and its complement "rx_in(n)" which the fitter autmoatically assigns, will be converted into a single serial bitstream by the LVDS I/O pair and presented to my deserializer as one rx_in?

[Altera_Forum]

Stratix and Arria have on-chip differential termination, Cyclone III (as other Cyclone family chips) hasn't. Where do you see a different statement in device literature?  

 The inverted input is assigned by the fitter automaticly, as you said. You have a single rx_in port pin representing the differential pair.

[Altera_Forum]

Thanks. In the Cyclone III Device Handbook, High Speed Differential I/O section, it was not clearly stated that an external 100Ohm resistor was required at the input of the LVDS receiver pins. There are clear statements about the requirement of external resistor networks for LVDS transmitter.

[Altera_Forum]

I agree, that the requirement of external differential termination may be not that obvious. 

 However, there is a figure 8–2. typical lvds application, that shows the external termination. The verbose discussion of transmitter termination networks is necessary because of the different handling in row and column banks.  If you are migrating from Cyclone or Cyclone II, you probably expect, that an external termination is necessary as with the predecessor, if you used Stratix before, you may expect an on-chip termination.

[Altera_Forum]

How do I set termination for LVDS Receiver in QuartusII 8.1. I'm using Stratix III FPGA. 

Thanks!

[Altera_Forum]

In Pin Planner (you have to add a respective column from the right-mouse context menu) or Assignment Editor.

[Altera_Forum]

Got it. It works. 

 One more question if I may:   Regarding the 100 ohms differential termination on the LVDS input.   What is the keyword to be selected on the "Input Termination" column?  - OCT 100 ohms or - Differential or  - Other (please specify)   What about the "Termination Control" column?   Thanks!

[Altera_Forum]

Choose differential for LVDS inputs.

[Altera_Forum]

--- Quote Start ---  Choose differential for LVDS inputs.  --- Quote End ---     Leave "Termination Control Block Column" blank? This column doesn't have pull down options.   Thanks!

[Altera_Forum]

Funny, I can't see that column in my assignment editor or pin planner and I'm on 8.1. Where is it you see this column?

[Altera_Forum]

Initially, it was not on my either. 

 Right click on any column,   Select "Customize columns" Add "Termination control Block"   I'm assuming your project is already set to Stratix III. I'm not familiar with other parts so I don't know if the have this option.   Thanks!

[Altera_Forum]

It's not relevant since the differential inputs have dedicated terminations. The TCBs are for dynamic termination.

[Altera_Forum]

--- Quote Start ---  It's not relevant since the differential inputs have dedicated terminations. The TCBs are for dynamic termination.  --- Quote End ---     Got it. Thank you very much for your help. :)