Motorola MCF5281 ユーザーズマニュアル

MOTOROLA

Chapter 9.  Clock Module  

9-3

There is also a fast wakeup option for quickly enabling the system clocks during stop
recovery. This eliminates the wakeup recovery time but at the risk of sending a potentially
unstable clock to the system. To prevent a non-locked PLL frequency overshoot when using
the fast wakeup option, change the RFD divisor to the current RFD value plus one before
entering stop mode.

In external clock mode, there are no wakeup periods for oscillator startup or PLL lock.

Figure  shows a block diagram of the entire clock module. The PLL block in this diagram
is expanded in detail in Figure 9-2.

.

CLKOUT

XTAL

EXTERNAL CLOCK

OSC

PLLREF

REFERENCE

CLOCK

PLL

MFD

PLLMODE

LOCEN

CLKMOD[1:0]

RSTOUT

CLKOUT

LOCKS

LOCK

LOCS

RFD[2:0]

TO RESET

MODULE

LOLRE

LOCRE

STPMD[1:0]

STOP MODE

PLLSEL

DISCLK

PLL CLOCK OUT

SCALED PLL CLOCK OUT

INTERNAL CLOCK

PLLMODE

CLKGEN

STOP MODE

INTERNAL

CLOCKS

LOCK

FWKUP

EXTAL