Block Diagram - Motorola ColdFire MCF5281 User Manual

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.
9.4

Block 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.
.
EXTAL XTAL
EXTERNAL CLOCK
OSC
STPMD[1:0]
STOP MODE
MOTOROLA
CLKMOD[1:0]
REFERENCE
CLOCK
PLLREF LOCEN
CLKGEN
PLLSEL
PLLMODE
Figure 9-1. Clock Module Block Diagram
Chapter 9. Clock Module
RSTOUT CLKOUT
MFD PLLMODE
PLL
LOLRE LOCRE
PLL CLOCK OUT
SCALED PLL CLOCK OUT
INTERNAL CLOCK
DISCLK
STOP MODE
LOCK
FWKUP
Block Diagram
LOCKS
LOCK
LOCS
RFD[2:0]
TO RESET
MODULE
CLKOUT
INTERNAL
CLOCKS
9-3