The preload values used in the implementation of your design depend on the INIT=R/S attribute. The INIT attribute specifies the initialization value to be preloaded into a register upon power-up. INIT=R specifies a preload value of 0 (reset) and INIT=S specifies a preload value of 1 (set). This attribute can be applied to flip-flops or any component containing a register. The initial state of all flip-flops in an XC9000 design is zero unless otherwise specified by INIT=S.
The only differences expected between functional and timing simulation involve the initial states of registers and latches. When you perform functional simulation directly from your schematic, the simulation models for each registered symbol have no knowledge of any INIT attributes you may have attached to the symbol. Therefore, functional simulation assumes that all preload values are zero. Timing simulation uses the actual preload values implemented by the fitter.
