MPC5604B/C Microcontroller Reference Manual, Rev. 8
Freescale Semiconductor 179
8.4.3.19 Clock Sources Switch-Off
Based on the device mode and the <clock source>ON bits of the ME_<mode>_MC registers, if a given
clock source is to be switched off, the MC_ME requests the clock source to power down and updates its
availability status bit S_<clock source> of the ME_GS register to ‘0’.
This step is executed only after
• System Clock Switching process is completed in order not to lose the current system clock during
mode transition.
• FMPLL Switch-Off as the input reference clock of the FMPLL can be among these clock sources.
This is needed to prevent an unwanted lock transition when the FMPLL is switched on.
8.4.3.20 Flash Switch-Off
Based on the CFLAON and DFLAON bit fields of the ME_<current mode>_MC and
ME_<target mode>_MC registers, if any of the flash modules is to be put in a low-power state, the
MC_ME requests the flash to enter the corresponding low-power state and waits for the deassertion of
flash ready status signal. The exact low-power mode status of the flash modules is updated in the S_CFLA
and S_DFLA bit fields of the ME_GS register. This step is executed only when Processor and System
Memory Clock Disable process is completed.
8.4.3.21 Main Voltage Regulator Switch-Off
Based on the MVRON bit of the ME_<current mode>_MC and ME_<target mode>_MC registers, if the
main voltage regulator is to be switched off, the MC_ME requests it to power down and clears the
availability status bit S_MVR of the ME_GS register.
This step is required only during the entry of low-power modes like HALT and STOP. This step is executed
only after completing the following processes:
• FMPLL Switch-Off
• Flash Switch-Off
• Power Domain #2 Switch-Off
• Power Domain #2 Switch-On
• the device consumption is less than the pre-defined threshold value (i.e. the S_DC bit of the
ME_GS register is ‘0’).
If the target mode is STANDBY, the main voltage regulator is not switched off by the MC_ME and the
STANDBY request is asserted after the above processes have completed upon which the MC_PCU takes
control of the main regulator. As the MC_PCU needs the 16 MHz int. RC osc., the fast internal RC
oscillator (16 MHz) remains active until all the STANDBY steps are executed by the MC_PCU after which
it may be switched off depending on the FIRCON bit of the ME_STANDBY_MC register.
8.4.3.22 Current Mode Update
The current mode status bit field S_CURRENT_MODE of the ME_GS register is updated with the target
mode bit field TARGET_MODE of the ME_MCTL register when:
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