Motorola ColdFire MCF5281 - Manual (Page 141)

Power Management
Freescale Semiconductor 7-5
NOTE
If LPCR[LPMD] is cleared, then the device stops executing code upon issue
of a STOP instruction. However, no clocks are disabled.
7.3 Functional Description
The functions and characteristics of the low-power modes, and how each module is affected by, or affects,
these modes are discussed in this section.
7.3.1 Low-Power Modes
The system enters a low-power mode by executing a STOP instruction. Which mode the device actually
enters (either stop, wait, or doze) depends on what is programmed in LPCR[LPMD]. Entry into any of
these modes idles the CPU with no cycles active, powers down the system and stops all internal clocks
appropriately. During stop mode, the system clock is stopped low.
For entry into stop mode, the LPICR[ENBSTOP] bit must be set before a STOP instruction is issued.
A wakeup event is required to exit a low-power mode and return to run mode. Wakeup events consist of
any of these conditions:
• Any type of reset
• Any valid, enabled interrupt request
The latter method of exiting from low-power mode, by a valid and enabled interrupt request, requires
several things:
• An interrupt request whose priority is higher than the value programmed in the XLPM_IPL field
of the LPICR
• An interrupt request whose priority higher than the value programmed in the interrupt priority
mask (I) field of the core’s status register
• An interrupt request from a source which is not masked in the interrupt controller’s interrupt mask
register
• An interrupt request which has been enabled at the module of the interrupt’s origin
7.3.1.1 Run Mode
Run mode is the normal system operating mode. Current consumption in this mode is related directly to
the system clock frequency.
Table 7-6. PLL/CLKOUT Stop Mode Operation
STPMD[1:0]
Operation During Stop Mode
System Clocks CLKOUT PLL OSC PMM
00 Disabled Enabled Enabled Enabled Enabled
01 Disabled Disabled Enabled Enabled Enabled
10 Disabled Disabled Disabled Enabled Enabled
11 Disabled Disabled Disabled Disabled Low-Power Option
MCF5282 and MCF5216 ColdFire Microcontroller User’s Manual, Rev. 3