AR# 1942: XC4000XL: VTT connections on 4000XL pinouts...
XC4000XL: VTT connections on 4000XL pinouts...
Keywords: vtt, pinout, xl
VTT connections were initially anticipated in the preliminary XL pinouts to be IO voltage level connections to allow the 3.3volt XL devices, and future voltage migrations, to properly interface the IO to other 5 volt devices. Later testing showed that these were not necessary for the 3.3 volt parts. As a result the VTT connections for the 3.3volt XL parts were left unbonded (N.C.).
These VTT pins may become VCC connections later on so, users can either leave them unconnected, or tie them to VCC.