MPC563XM Reference Manual, Rev. 1
Freescale Semiconductor
573
Preliminary—Subject to Change Without Notice
LOCEN and LOCRE have no effect in bypass mode. If the reference fails while the FMPLL is in bypass
mode with crystal reference, a system reset is asserted regardless of the state of LOCEN and LOCRE.
Since bypass is the FMPLL reset mode, the crystal oscillator must be present and functioning properly to
exit reset when PLLREF=1. When PLLREF=0, the reference clock is not checked for loss-of-clock, so exit
from reset can happen regardless the state of the reference clock. Exit from reset is not affected by the state
of the FMPLL output because the FMPLL clock is not monitored in bypass mode.
17.5.4.3
Loss-of-Clock Interrupt Request
When a loss-of-clock condition is recognized, an interrupt request may be asserted depending on the clock
operating mode and control bits in the FMPLL registers, as shown in
.
LOCEN and LOCIRQ have no effect in bypass mode. If the reference fails in bypass mode with crystal
reference, a system reset is asserted instead of an interrupt request. If the reference fails in bypass with
external reference, no reset or interrupts are generated. Furthermore, no reset or interrupts are generated
when lock is lost due to a write to the SYNCR in legacy mode which modifies the PREDIV or MFD fields,
or a write to ESYNCR1 in enhanced mode which modifies the EMODE, EPREDIV, EMFD or
CLKCFG[1:0] fields.
Normal mode with crystal reference
0
—
No
No
1
0
No
No
1
1
Yes
Yes
1
LOCEN is the loss-of-clock enable bit in either SYNCR or ESYNCR2, depending on the ESYNCR1[EMODE] bit.
2
LOCRE is the loss-of-clock reset enable bit in either SYNCR or ESYNCR2, depending on the ESYNCR1[EMODE] bit.
Table 17-13. Loss-of-Clock Reset (continued)
Operating Mode
LOCEN
1
LOCRE
2
Reset
Reference Failure
FMPLL Failure