Motorola MCF5281, MCF5282 user manual Clock Module Block Diagram

Block Diagram

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.

9.4Block Diagram

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

.
		CLKMOD[1:0]		RSTOUT	CLKOUT
EXTAL	XTAL					LOCKS
			MFD	PLLMODE
EXTERNAL CLOCK						LOCK
	REFERENCE
	CLOCK			PLL		LOCS
OSC						RFD[2:0]
						TO RESET
						MODULE
	PLLREF	LOCEN		LOLRE	LOCRE
				PLL CLOCK OUT
STPMD[1:0]
					SCALED PLL CLOCK OUT
STOP MODE	CLKGEN				INTERNAL CLOCK	CLKOUT
	PLLSEL		DISCLK
						INTERNAL
						CLOCKS
					STOP MODE
	PLLMODE			LOCK
				FWKUP

Figure 9-1. Clock Module Block Diagram

MOTOROLA Chapter 9. Clock Module 9-3