Honored Contributor
Honored ContributorSeems like you never consulted the Cyclone II LVDS specification. Unlike Cyclone III or high end FPGA, Cyclone II doesn't provide a true LVDS driver. It needs external resistors, either in the 3R (Device Handbook Figure 11-3) or the 1R/RSDS configuration (Figure 11-7). In addition, a 100 ohm differential load at the receiver must be present to get the correct LVDS level.
The DE2-70 board isn't actually wired for differential signaling. You have additional 47 ohm series resistors in the input protection network that must be taken into consideration.
