Optimum power management of system on chip based on tiered states of operation is disclosed. In one embodiment, a system on chip includes a hardware module including one or more of a microcontroller, a microprocessor, a DSP core, a memory, a timing source, a peripheral, and an external interface to have a real time counter module of the peripheral isolated from a rest of the hardware module using a plurality of voltage level shifting cells and/or a plurality of voltage island cells. Also, the system on chip includes a software module associated with the real time counter module to generate one or more control signals to one or more devices external to the system on chip during a sleep mode of the system on chip.