PXD20RM Datasheet, PDF (1104/1628 Pages) Freescale Semiconductor, Inc – PXD20 Microcontroller

Table 29-17. MC_ME System Clock Selection Overview (continued)
System
Clock
Source
RESET
TEST
SAFE
Mode
DRUN RUN0…3
HALT
STOP
primary

PLL/2



system
^

clock is
disabled
1 _{disabling the system clock during TEST mode will require a reset in order to exit TEST mode}
STANDBY

(default)
29.4.3.16 Power Domain #2 Switch-Off
Based on the device mode and the MC_PCU’s power configuration register PCU_PCONF2, the power
domain #2 is controlled by the MC_PCU.
If a mode change translates to a power-down of the power domain, then the MC_PCU starts the
power-down sequence. The MC_PCU acknowledges the completion of the power-down sequence with
respect to the new mode, and the MC_ME uses this information to update the mode transition status. This
step is executed only after the Peripheral Clocks Disable process has completed.
29.4.3.17 Pad Switch-Off
If the PDO bit of the ME_<target mode>_MC register is ‘1’ then
• the outputs of the pads are forced to the high impedance state if the target mode is SAFE or TEST
• I/O pads power sequence driver is switched off if the target mode is one of SAFE, TEST, or STOP
modes
In STANDBY mode, the power sequence driver and all pads except the external reset and those mapped
on wakeup lines are not powered and therefore high impedance. The wakeup line configuration remains
unchanged.
This step is executed only after the Peripheral Clocks Disable process has completed.
29.4.3.18 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’. The following clock sources
switched off at this step:
This step is executed only after the System Clock Switching process has completed.
29.4.3.19 Flash Switch-Off
Based on the FLAON bit field of the ME_<current mode>_MC and ME_<target mode>_MC registers,
if the flash is to be put in its low-power or power-down mode, the MC_ME requests the flash to enter the
29-46
PXD20 Microcontroller Reference Manual, Rev. 1
Preliminary—Subject to Change Without Notice
Freescale Semiconductor