PXS20RM Datasheet, PDF (1093/1368 Pages) Freescale Semiconductor, Inc – PXS20 Microcontroller

Mode Entry Module (MC_ME)
32.4.2.7 STOP0 mode
The device enters this mode on the following events:
• From one of the RUN0…3 modes when the TARGET_MODE bit field of the ME_MCTL register
is written with “1010”.
As soon as any of the above events has occurred, a STOP0 mode transition request is generated. The mode
configuration information for this mode is provided by the ME_STOP0_MC register. This mode is fully
configurable, and the ME_STOP0_MC register should be programmed according to the system needs. The
following clock sources are switched off in this mode:
• The system FMPLL
• The secondary FMPLL
The flash can be put in power-down mode as needed. If there is a STOP0 mode request while any interrupt
or wakeup event is active, the transition to STOP0 is aborted with the resultant mode being the current
mode, SAFE (on SAFE mode request), or DRUN (on reset), and an invalid mode interrupt is not generated.
This can be used as an advanced low-power mode with the core clock frozen and almost all peripherals
stopped.
This mode is intended as an advanced low-power mode with
• The core clock frozen
• Almost all peripherals stopped
and to be used by software
• To wait until it is required to do something with no need to react quickly (e.g. allow for system
clock source to be re-started)
This mode can be used to stop all clock sources and thus preserve the device status. When exiting the
STOP0 mode, the 16 MHz internal RC oscillator clock is selected as the system clock until the target clock
is available.
NOTE
For cut2/3: It is good practice for software to ensure that the S_MTRANS
bit in the register has been cleared on STOP0 mode exit to ensure that the
previous RUN0…3 mode configuratoin has been fully restored before
executing critical code.
32.4.3 Mode transition process
The process of mode transition follows the following steps in a pre-defined manner depending on the
current device mode and the requested target mode. In many cases of mode transition, not all steps need
to be executed based on the mode control information, and some steps may not be applicable according to
the mode definition itself.
Freescale Semiconductor
PXS20 Microcontroller Reference Manual, Rev. 1
32-37