For the Lattice MachXO device, all the registers in the device will be reset upon power-up of the device, provided the power-up sequence is clean. This will happen without any additional effort on the part of the user.

The software will evaluate the design and if there are register resets present, it will usually assign one of them to the GSR resource in the device. This GSR resource consists of a preferred routing path for the reset signal within the device but this is NOT automatically connected to the GSRN pin in the device. This preferred routing resource has lower skew than general purpose routing so it provides a better path for resetting registers that are distributed throughout the device.

If the user is driving the reset from an input pin then they can assign that signal to the GSRN pin. The advantage of doing this is that the GSRN input pin provides a fast access path to the GSR routing resource in the device. (Note that a reset signal that is tied to the GSRN pin does not have to be active low. However it is recommended to make it active low to match the pin designation.) All this happens without using the GSR schematic symbol in a design (or the GSR component in a VHDL or Verilog design).

The GSR component is typically only used for simulation for VHDL or Verilog designs though is can also be used to specify which signal the user wants to use for GSR in the design.

For a schematic design you could use the GSR schematic symbol to specify which signal you want to use for the GSR but you must remember that GSR is active low by definition in the schematic symbol. For the LatticeMachXO you could also specify the signal to use for GSR with a preference if necessary so you do not have to use the schematic symbol to do this. The GSR symbol is not required for simulation in a schematic design.