AR# 1423: XC3000/XC4000: Are the internal tri-state busses(3k,4k) PULLED Up by default?
XC3000/XC4000: Are the internal tri-state busses(3k,4k) PULLED Up by default?
Keywords: Tristate, BUFT, BUFE, XC3000, XC4000
Description Internal tri-state bus for 3k and 4k families does not have pullups on the outputs by default.
For a schematics based design, connect a PULLUP symbol on the outputs of the internal tri-state bus. For a behavioral design, instantiate a PULLUP primitive. Refer to the appropriate Interface Guide for more information.