Embodiments of the present invention provide a flash memory device with a unified oscillation circuit, and a method of operating the device. The unified oscillation circuit produces alternative internal clock signals for corresponding alternative operating modes of the flash memory device. At least a portion of the unified oscillation circuit is used to generate all of the alternative internal clock signals. Compared to conventional memory devices and methods that use multiple oscillators, embodiments of the invention improve circuit density and reduce the incidence of timing glitches caused by switching between multiple oscillators.