Stop Mode Operation - Motorola ColdFire MCF5281 User Manual

A special loss-of-clock condition occurs when both the reference and the PLL fail. The
failures may be simultaneous, or the PLL may fail first. In either case, the reference clock
failure takes priority and the PLL attempts to operate in SCM. If successful, the PLL
remains in SCM until the next reset. If the PLL cannot operate in SCM, the system remains
static until the next reset. Both the reference and the PLL must be functioning properly to
exit reset.
9.7.4.11 Loss of Clock in Stop Mode
Table 9-10 shows the resulting actions for a loss of clock in Stop Mode when the device is
being clocked by the various clocking methods.
Table 9-10. Stop Mode Operation (Sheet 1 of 5)
MODE
In
EXT X X X X X
NRM 0 0 0 Off Off 0 Lose lock,
NRM X 0 0 Off Off 1 Lose lock,
MOTOROLA
Expected
PLL PLL Action
Action at During Stop
Stop
X — —
Lose reference
clock
Regain
f.b. clock,
No regain
reference
clock
Regain clocks, but
f.b. clock, don't regain lock
reference
clock
No reference clock
regain
No f.b. clock
regain
Chapter 9. Clock Module
MODE
Out
EXT 0 0
Stuck — —
NRM 'LK 1
Stuck — —
SCM–> 0–>'L 0–>1 1–>'L
unstable K
NRM
SCM–> 0–> 0–>
Stuck — —
Functional Description
Comments
0
—
'LC
—
Block LOCS and
C LOCKS until
clock and lock
respectively
regain; enter
SCM regardless
of LOCEN bit
until reference
regained
1–> Block LOCS and
LOCKS until
clock and lock
respectively
regain; enter
SCM regardless
of LOCEN bit
—
9-17