According to embodiments of the invention, a nonvolatile memory such as a flash memory is used to configure a single die after packaging of the die has occurred. Thus, numerous applications may be supported by a single die or optimization within a given application may occur. According to embodiments of the invention, the nonvolatile memory may be accessed through a programming interface, and preferably, through a two-pin programming interface, to normalize parameters such as package parasitics, crystal variations, output dividers, output duty cycle, output edge rates, I/O configuration, and oscillator gain. According to an embodiment of the invention, an XO circuit configuration includes a nonvolatile memory and a stand-alone XO, where the XO circuit configuration does not require a PLL to synthesize a reference frequency produced by the XO.