Power Management
MCF52277 Reference Manual, Rev. 1
Freescale Semiconductor
8-11
8.3.4.3
Clock Module
In wait and doze modes, the clocks to the CPU and SRAM stop and the system clocks to the peripherals
enable. Each module may disable the module clocks locally at the module level, or the module clocks may
be individually disabled by the PPMR registers (refer to
Section 8.2.4, “Peripheral Power Management
). In stop mode, all clocks to the system stop.
There are several options for enabling or disabling the PLL or crystal oscillator in stop mode,
compromising between stop mode current and wake-up recovery time. The PLL can be disabled in stop
mode, but requires a wake-up period before it can relock. The oscillator can also be disabled during stop
mode, but requires a wake-up period to restart.
When the PLL is enabled in stop mode (LPCR[STPMD] equals 00), the external FB_CLK signal can
support systems using FB_CLK as the clock source. See
Section 8.2.5, “Low-Power Control Register
for more information about operating the PLL in stop mode.
There is also a fast wake-up option for quickly enabling the system clocks during stop recovery
(LPCR[FWKUP]). This eliminates the wake-up recovery time but at the risk of sending a potentially
unstable clock to the system. This is also explained in
Section 8.2.5, “Low-Power Control Register
8.3.4.4
Chip Configuration Module
The chip configuration module is unaffected by entry into a low-power mode. If a reset exits low-power
mode, chip configuration may execute if configured to do so.
8.3.4.5
Reset Controller
A power-on reset (POR) always causes a chip to reset and exit from any low-power mode.
In wait and doze modes, asserting the external RESET pin for at least four clocks causes an external reset
that resets the chip and exits any low-power modes.
In stop mode, the RESET pin synchronization disables and asserting the external RESET pin
asynchronously generates an internal reset and exit any low-power modes. Registers lose current values
and must be reconfigured from reset state if needed.
If the core watchdog timer remains enabled during wait or doze modes, a watchdog timer timeout may
generate a reset to exit these low-power modes.
When the CPU is inactive, a software reset cannot generate to exit any low-power mode.
8.3.4.6
System Control Module (SCM)
The SCM’s core watchdog timer can bring the device out of all low-power modes except stop mode. In
stop mode, all clocks stop, and the core watchdog timer does not operate.
When enabled, the core watchdog can bring the device out of low-power mode in one of two ways.
Depending on the setting of the CWCR[CWRI] field, a core watchdog timeout may reset the device. Other
settings of the CWRI field may enable a core watchdog interrupt and upon a watchdog timeout, this
Содержание MCF52277
Страница 1: ...MCF52277 Reference Manual Devices Supported MCF52274 MCF52277 Document Number MCF52277RM Rev 1 04 2008...
Страница 22: ...MCF52277 Reference Manual Rev 1 Freescale Semiconductor xxii...
Страница 32: ...MCF52277 Reference Manual Rev 0 xxxii Freescale Semiconductor...
Страница 60: ...Signal Descriptions MCF52277 Reference Manual Rev 1 2 16 Freescale Semiconductor...
Страница 112: ...Enhanced Multiply Accumulate Unit EMAC MCF52277 Reference Manual Rev 1 4 20 Freescale Semiconductor...
Страница 128: ...Static RAM SRAM MCF52277 Reference Manual Rev 1 6 6 Freescale Semiconductor...
Страница 140: ...Clock Module MCF52277 Reference Manual Rev 1 7 12 Freescale Semiconductor...
Страница 172: ...Chip Configuration Module CCM MCF52277 Reference Manual Rev 1 9 16 Freescale Semiconductor...
Страница 180: ...Serial Boot Facility SBF MCF52277 Reference Manual Rev 1 10 8 Freescale Semiconductor...
Страница 188: ...Reset Controller Module MCF52277 Reference Manual Rev 1 11 8 Freescale Semiconductor...
Страница 210: ...Crossbar Switch XBS MCF52277 Reference Manual Rev 1 13 8 Freescale Semiconductor...
Страница 480: ...Liquid Crystal Display Controller LCDC MCF52277 Reference Manual Rev 1 21 44 Freescale Semiconductor...
Страница 510: ...Touchscreen Controller Analog to Digital Converter MCF52277 Reference Manual Rev 1 22 30 Freescale Semiconductor...
Страница 542: ...FlexCAN MCF52277 Reference Manual Rev 1 23 32 Freescale Semiconductor...
Страница 568: ...Pulse Width Modulation PWM Module MCF52277 Reference Manual Rev 1 24 26 Freescale Semiconductor...
Страница 640: ...Programmable Interrupt Timers PIT0 PIT1 MCF52277 Reference Manual Rev 1 27 8 Freescale Semiconductor...
Страница 690: ...DMA Serial Peripheral Interface DSPI MCF52277 Reference Manual Rev 1 29 40 Freescale Semiconductor...
Страница 724: ...UART Modules MCF52277 Reference Manual Rev 1 30 34 Freescale Semiconductor...
Страница 740: ...I2 C Interface MCF52277 Reference Manual Rev 1 31 16 Freescale Semiconductor...
Страница 790: ...Debug Module MCF52277 Reference Manual Rev 1 32 50 Freescale Semiconductor...