Chapter 7 Mode Entry Module (MC_ME)
MPC5602P Microcontroller Reference Manual, Rev. 4
166
Freescale Semiconductor
Section 7.4.6, “Peripheral Clock Gating“
for more details.
Each peripheral that may block or disrupt a communication bus to which it is connected ensures that these
outputs are forced to a safe or recessive state when the device enters the SAFE mode.
7.4.3.4
Processor Low-Power Mode Entry
If, on completion of the
step, the mode transition is to the HALT0 mode, the
MC_ME requests the processor to enter its halted state. The processor acknowledges its halt state request
after completing all outstanding bus transactions.
If, on completion of the
step, the mode transition is to the STOP0 mode, the
MC_ME requests the processor to enter its stopped state. The processor acknowledges its stop state request
after completing all outstanding bus transactions.
7.4.3.5
Processor and System Memory Clock Disable
If, on completion of the
Processor Low-Power Mode Entry
step, the mode transition is to the HALT0 or
STOP0 mode and the processor is in its appropriate halted or stopped state, the MC_ME disables the
processor and system memory clocks to achieve further power saving.
The clocks to the processor and system memory are unaffected while transitioning between software
running modes such as DRUN, RUN0…3, and SAFE.
WARNING
Clocks to the whole device including the processor and system memory can
be disabled in TEST mode.
7.4.3.6
Clock Sources Switch-On
Processor Low-Power Mode Entry
step, the MC_ME switches on all clock sources
based on the <clock source>ON bits of the ME_<current mode>_MC and ME_<target mode>_MC
registers. The following clock sources are switched on at this step:
•
the 16 MHz internal RC oscillator
•
the 4 MHz crystal oscillator
•
the system PLL
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 clocks is updated in the S_<clock source> bits of ME_GS register.
The clock sources which 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.