Freescale Semiconductor MCF52277 Reference Manual page 153

8.3.4.12 FlexBus Module
In wait and doze modes, the FlexBus module continues operation but does not generate interrupts;
therefore, it cannot bring a device out of a low-power mode. This module is stopped in STOP mode.
8.3.4.13 SDRAM Controller (SDRAMC)
SDRAM controller operation is unaffected by wait or doze modes; however, the SDRAMC is disabled by
stop mode. Because the STOP mode disables all clocks to the SDRAMC, the SDRAMC does not generate
refresh cycles.
To prevent data loss, SDRAMC should be placed in self-refresh mode by clearing SDCR[CKE] and setting
SDCR[REF_EN]. The SDRAM self-refresh mode allows the SDRAM to enter a low-power state where
internal refresh operations maintain the integrity of the SDRAM data.
When stop mode is exited, setting the SDCR[CKE] bit causes the SDRAM controller to exit the
self-refresh mode and allow bus cycles to the SDRAM to resume.
The SDRAM is inaccessible in the self-refresh mode. Therefore, if stop
mode is used, the vector table and any interrupt handlers that could wake the
processor should not be stored in or attempt to access SDRAM.
8.3.4.14 USB On-the-Go Module
If the USB On-the-Go module is clocked externally, it operates normally in wait mode. It is capable of
generating an interrupt to wake-up the core from wait mode. In stop and doze mode, the USB module is
disabled.
The USB block contains an automatic low-power mode in which the module enters suspend mode after a
6.0 ms minimum period of inactivity. When the module receives a wake-up from the USB host, the
transceiver is re-enabled for normal USB operations.
8.3.4.15 Touchscreen Controller/ADC
The touchscreen controller operates normally in wait mode, and if the ASP_CR[DOZE] bit is cleared, it
also operates normally in doze mode. If in doze mode and ASP_CR[DOZE] is set, the clock is disabled
after the current conversion is complete.
In stop mode, the touschreen controller is disabled and the current conversion is stopped immediately no
matter if the current conversion is complete. It is recommended to clear ASP_CR[ASPE] before entering
stop mode.
The touchscreen controller is capable of generating an interrupt to wake-up the core from wait and doze
modes. In stop mode, there is a pen-down event that can generate an interrupt to wake-up the device. Upon
exiting stop mode, the touschreen controller resumes operation from the state prior to stop mode entry.
Freescale Semiconductor
NOTE
MCF52277 Reference Manual, Rev. 1
Power Management
8-13