Apparatus and methods for controlling a clock signal are provided. In certain embodiments, a semiconductor die includes a core circuit and a clock interface circuit that provides a clock signal to the core circuit. The clock interface circuit includes an oscillator for generating an oscillator signal, and a comparator for controlling operation of the clock interface circuit in a selected clock control mode based on comparing an electrical characteristic of the clock interface pin to a comparison threshold. The selected clock control mode is chosen from a first clock control mode in which the clock interface circuit generates the clock signal based on an input clock signal received on a clock interface pin, or a second clock control mode in which the clock interface circuit generates the clock signal based on the oscillator signal.