Power Control Unit (MC_PCU)MPC5606S Microcontroller Reference Manual, Rev. 7990 Freescale SemiconductorEach power domain which is powered down is held in a reset state. Read/write accesses to peripherals inthose power domains will result in a transfer error.29.4.4 Mode transitionsOn a mode change requested by the MC_ME, the MC_PCU evaluates the power configurations for allpower domains. It compares the settings in the PCU_PCONFn registers for the new mode with the settingsfor the current mode. If the configuration for a power domain differs between the modes, a power statechange request is generated. These requests are handled by a finite state machine to ensure a smooth andsafe transition from one power state to another.29.4.4.1 DRUN, Safe, Test, Run0…3, Halt, and Stop mode transitionThe DRUN, Safe, Test, Run0…3, Halt, and Stop modes allow an increased power saving. The level ofpower saving is software-controllable via the settings in the PCU_PCONFn registers for power domain #2onwards. The settings for power domains #0 and #1 cannot be changed. Therefore, power domains #0 and#1 remain connected to the power supply for all modes beside Standby.Figure 29-6 shows an example for a mode transition from Run0 to Halt and back, which will result inpower domain #2 being powered down during the Halt mode. In this case, PCU_PCONF2.HALT isprogrammed to be 0.When the MC_PCU receives the mode change request to Halt mode, it starts its power-down phase.During the power-down phase, clocks are disabled and the reset is asserted resulting in a loss of allinformation for this power domain.Then the power domain is disconnected from the power supply (power-down state).Figure 29-6. MC_PCU Events During Power Sequences (non-Standby mode)When the MC_PCU receives a mode change request to Run0, it starts its startup phase ifPCU_PCONF2.RUN0 is 1. The power domain is re-connected to the power supply, and the voltage innew modepower-downRUN0voltage inPSTAT.PD2HALT RUN0Notes:Not drawn to scale; PCONF2.RUN0 = 1; PCONF2.HALT = 0current modestartup phasepower domain #2RUN0 HALT RUN0requested by MEpower-down state startup statestartup statephase
