NXP Semiconductors MPC5605BK, Reference Manual

Page: 170 / 964

Chapter 8 Mode Entry Module (MC_ME)
MPC5606BK Microcontroller Reference Manual, Rev. 2
170 Freescale Semiconductor
8.4.3.6 Clock sources switch-on
On completion of the Processor low-power mode entry , the MC_ME controls all clock sources that affect
the system clock based on the <clock source> ON bits of the ME_ <current mode> _MC and
ME_ <target mode> _MC registers. The following system clock sources are controlled at this step:
• The fast internal RC oscillator (16 MHz)
The clock sources that are required by the target mode are switched on. The duration required for the
output clocks to be stable depends on the type of source, and all further steps of mode transition depending
on one or more of these clocks waits for the stable status of the respective clocks. The availability status
of these system clocks is updated in the S_
<clock source> bits of ME_GS register.
The clock sources that need to be switched off are unaffected during this process in order to not disturb the
system clock, which might require one of these clocks before switching to a different target clock.
It is also possible to automatically switch-on the FXOSC after exiting STANDBY mode, by programming
ME_DRUN_MC[FXOSC] = 1 prior to STANDBY entry. After the chip exits STANDBY mode, your
software should wait for FXOSC to be switched-on before any mode transition request in order to avoid a
mode request illegal event.
8.4.3.7 Main voltage regulator switch-on
On completion of the Target mode request , if the main voltage regulator needs to be switched on from its
off state based on the MVRON bit of the ME_ <current mode> _MC and ME_ <target mode> _MC
registers, the MC_ME requests the MC_PCU to power-up the regulator and waits for the output voltage
stable status in order to update the S_MVR bit of the ME_GS register.
This step is required only during the exit of the low-power modes HALT and STOP. In this step, the fast
internal RC oscillator (16 MHz) is switched on regardless of the target mode configuration, as the main
voltage regulator requires the 16 MHz int. RC osc. during power-up in order to generate the voltage status.
8.4.3.8 Flash modules switch-on
On completion of the Main voltage regulator switch-on , if a flash module needs to be switched to normal
mode from its low-power or power-down mode based on the CFLAON and DFLAON bit fields of the
ME_
<current mode> _MC and ME_ <target mode> _MC registers, the MC_ME requests the flash to exit
from its low-power/power-down mode. When the flash modules are available for access, the S_CFLA and
S_DFLA bit fields of the ME_GS register are updated to 11 by hardware.
If the main regulator is also off in device low-power modes, then during the exit sequence, the flash is kept
in its low-power state and is switched on only when the
Main voltage regulator switch-on process has
completed.
CAUTION
It is illegal to switch the flashes from low-power mode to power-down mode
and from power-down mode to low-power mode. The MC_ME, however,
does not prevent this nor does it flag it.