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Power Management
Freescale Semiconductor
9-11
9.3.4.7
GPIO Ports
The GPIO ports are unaffected by entry into a low-power mode. These pins may impact low-power current
draw if they are configured as outputs and are sourcing current to an external load. If low-power mode is
exited by a reset, the state of the I/O pins reverts to their default direction settings.
9.3.4.8
Interrupt Controllers (INTC0, INTC1)
The interrupt controller is not affected by any of the low-power modes. All logic between the input sources
and generating the interrupt to the processor is combinational to allow the ability to wake up the core
during low-power stop mode when all system clocks stop.
An interrupt request causes the processor to exit a low-power mode only if that interrupt’s priority level is
at or above the level programmed in the interrupt priority mask field of the CPU’s status register (SR) and
above the level programmed in the WCR[PRILVL]. The interrupt must also be enabled in the interrupt
controller’s interrupt mask register as well as at the module from which the interrupt request would
originate.
9.3.4.9
Edge Port
In wait and doze modes, the edge port continues to operate normally and may be configured to generate
interrupts (either an edge transition or low level on an external pin) to exit the low-power modes.
In stop mode, no system clock is available to perform the edge detect function. Therefore, only the level
detect logic is active (if configured) to allow any low level on the external interrupt pin to generate an
interrupt (if enabled) to exit stop mode.
9.3.4.10
eDMA Controller
In wait and doze modes, the eDMA controller can bring the device out of a low-power mode by generating
an interrupt upon completion of a transfer or upon an error condition. The completion of transfer interrupt
generates when DMA interrupts are enabled by the setting of a EDMA_INTR[INT
n
], and an interrupt is
generated when TCD
n
[DONE] is set. The interrupt upon error condition is generated when
EDMA_EEIR[EEI
n
] is set, and an interrupt generates when any of the EDMA_ESR bits become set.
The eDMA controller is stopped in stop mode and thus cannot cause an exit from this low-power mode.
9.3.4.11
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.
9.3.4.12
SDRAM Controller (SDRAMC)
SDRAM controller operation is unaffected either the 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.
Содержание MCF54455
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