Functional Description

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

 

 

 

 

 

 

 

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.

7.3Functional 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.

7.3.1Low-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

MOTOROLA

Chapter 7. Power Management

7-5

Page 173
Image 173
Motorola MCF5281, MCF5282 user manual Functional Description, Low-Power Modes, PLL/CLKOUT Stop Mode Operation