Multipoint LVDS backplane Bus using Stratix IV GT

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2. There is no tri-state control on the LVDS outputs, so you can not disable the transmitters without reconfiguring the FPGA.

This is the situation with the Stratix II FPGAs. I have not tested that this has changed on the Stratix IV, but I have not seen anything that indicates the LVDS design on the FPGAs has been changed.

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You better had read AN522 before writing this post. It's full title already suggests that the requested multipoint LVDS interface is well supported by Stratix IV:

"Implementing Bus LVDS Interface in Cyclone III, Stratix III, and stratix iv Devices"