Low-Power Modes; Cpu Core Low-Power Modes - Motorola M-CORE MMC2001 Series Reference Manual

8.2 Low-Power Modes

The MMC2001 supports the following features:
• Four low-power modes:
— Run
— Wait
— Doze
— Stop
• Ability to shut down all peripherals independently
• Ability to shut down the CLKOUT pin.

8.2.1 CPU Core Low-Power Modes

The CPU supports four low-power modes: run, wait, doze, and stop.
8.2.1.1 Run Mode
Run mode is the normal CPU operating mode. Current consumption in this mode is
related directly to the frequency chosen for the HI_REFCLK (16.38 MHz).
8.2.1.2 Wait Mode
Wait mode is intended to be used to stop only the CPU clock until an interrupt is
detected. In this mode, all peripherals continue operation and can generate inter-
rupts, which cause the CPU to exit from wait mode.
8.2.1.3 Doze Mode
Doze mode affects the CPU in the same manner as wait, but with a different code on
the CPU LPMD output signals, which are monitored by peripherals. Each peripheral
defines individual operational characteristics in doze mode. Peripherals which con-
tinue to run and have the capability of producing interrupts may cause the CPU to exit
the doze mode and return to the run mode. Peripherals which were stopped will
restart operation on exit from doze mode as defined for each peripheral.
8.2.1.4 Stop Mode
Stop mode affects the CPU in the same manner as wait, but with a different code on
the CPU LPMD output signals, which are monitored by peripherals. In this mode,
peripherals cease operation except for the PIT and watchdog timer, which may con-
tinue to run (if enabled) using prescaled versions of the LOW_REFCLK clock source.
The TOD timer is unaffected in this mode. Several sources exist to exit this mode and
return to the run mode. See Table 8-2 for more details.
Stopped peripherals stop after entering their individual reset states. When exiting
stop mode, most peripherals retain their pre-stop control register values and resume
operation. Stop mode must be entered in a controlled manner, by shutting down each
peripheral that is going to be stopped after it is ensured that its current operation is
properly terminated.
MOTOROLA
8-4
Freescale Semiconductor, Inc.
CLOCK MODULE AND LOW-POWER MODES
For More Information On This Product,
Go to: www.freescale.com
MMC2001
REFERENCE MANUAL