Data processing system with protocol determination circuitry

[0022]In one embodiment, an IC includes circuitry which is powered by a PMIC and circuitry which is powered by a low power source, such as a coin cell battery. The circuitry powered by the PMIC is located within an SoC power domain. The SoC may include any number and type of circuits which receive power provided by the PMIC. The circuitry powered by the low power source is located within a lower power domain, which may be referred to as a coin cell power domain. Upon initially applying power to the coin cell power domain, the circuitry within this domain determines the protocol of the PMIC. During this configuration phase, circuitry within the coin cell power domain provides test signals by way of an output pin to the PMIC and monitors the power provided by the PMIC to the IC in response to these test signals in order to determine the protocol of the PMIC. Determining the protocol of the PMIC includes determining whether the PMIC provides power in response to a toggle-mode signal or to