Motorola MCF5281 ユーザーズマニュアル
MOTOROLA
Chapter 7. Power Management
7-5
Functional Description
NOTE
If LPCR[LPMD] is cleared, then the MCF5282 will stop
executing code upon issue of a STOP instruction. However, no
clocks will be disabled.
executing code upon issue of a STOP instruction. However, no
clocks will be 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.
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.
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.
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:
events consist of any of these conditions:
• Any type of reset
• Any valid, enabled interrupt request
• Any valid, enabled interrupt request
Table 7-5. Low-Power Modes
LPMD[1:0]
Mode
11
STOP
10
WAIT
01
DOZE
00
RUN
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