What is the difference between the simulation signals
PRLD/MRESET and the signals used by the global buffers GTS
PRLD is simply a simulation signal only. During
configuration and power-up all flip flops in the device
are set to a known level, regardless of what the user does.
However, most timing simulators are unable to simulate this
behavior, thus PRLD must be used to initialize all
flip flops in the simulation.
For more details about PRLD see (Xilinx Solution 1045).
The GTS and GSR are global buffers that route to either
all Tri-state enables or all Set/Reset pins on flip flops
To simulate these signals in a simulation, stimulus must be
put on the net names.
The GTS and GSR buffers must be routed on schematic or
inferred in your HDL code to be used, unlike the GSR signal
found in Xilinx FPGAs.