
Frequency Modulated Phase-Locked Loop (FMPLL)
PXN20 Microcontroller Reference Manual, Rev. 1
7-12
Freescale Semiconductor
Figure 7-5. Lock Detect Sequence
After the PLL acquires lock after reset, the LOCK and LOCKS status bits are set. If the EPREDIV or
EMFD are changed, or if an unexpected loss-of-lock condition occurs, the LOCK and LOCKS status bits
are negated. While the PLL is in an unlocked condition, the system clocks continue to be sourced from the
PLL as the PLL attempts to re-lock. Consequently, during the re-locking process, the system clock
frequency is not well defined and may exceed the maximum system frequency violating the system clock
timing specifications. Because of this condition, use of the loss-of-lock reset function is recommended.
After the PLL has re-locked, the LOCK bit is set. The LOCKS bit remains cleared if the loss of lock was
unexpected. The LOCKS bit is set to one when the loss of lock was caused by changing the EPREDIV or
EMFD fields.
7.4.3.2
Loss-of-Clock Detection
When enabled by the LOCEN bit in the ESYNCR2, the loss-of-clock (LOC) detection circuit monitors the
input clocks to the phase/frequency detector (PFD) (see
). When the reference or feedback clock
frequency falls below a minimum frequency, the LOC circuitry considers the clock to have failed and a
loss-of-clock status is reflected by the sticky LOCF bit, and non-sticky LOC bit in the SYNSR. See
PXN20
Microcontroller Data Sheet
for the minimum clock frequency. In PLL Off mode, the loss-of-clock
circuitry is disabled.
Depending which clock source has failed, the LOC circuitry switches the PLL output clock’s source to the
remaining operational clock if enabled by LOCEN. The PLL output clocks are derived from the alternate
clock source until reset is asserted. The alternate clock source used is dependent on whether the LOC is
Count N + K
Reference cycles,
and compare
number of feed-
Lock detected
back cycles
Relax lock
criteria.
Reference count
equals N and feed-
back count equals N
in same count and
compare sequence.
Reference count
equals N + K and feed-
back count equals N + K
in same count and
compare sequence.
Alert system that
PLL has locked.
Feedback count does not
equal reference count of N or
N+K. Alert system that PLL
is not locked. Tighten
lock criteria.
Continue
monitoring PLL
with alternate
N and N+K count
and compare
sequences.
Count N
reference cycles,
and compare
number of feedback
cycles elapsed.
elapsed.
Содержание PXN2020
Страница 1: ...PXN20 Microcontroller Reference Manual Devices Supported PXN2020 PXN2120 PXN20RM Rev 1 06 2011...
Страница 42: ...PXN20 Microcontroller Reference Manual Rev 1 lxiv Freescale Semiconductor...
Страница 64: ...Introduction PXN20 Microcontroller Reference Manual Rev 1 1 22 Freescale Semiconductor...
Страница 112: ...Signal Description PXN20 Microcontroller Reference Manual Rev 1 3 44 Freescale Semiconductor...
Страница 118: ...Resets PXN20 Microcontroller Reference Manual Rev 1 4 6 Freescale Semiconductor...
Страница 162: ...Clocks Reset and Power CRP PXN20 Microcontroller Reference Manual Rev 1 6 30 Freescale Semiconductor...
Страница 182: ...Frequency Modulated Phase Locked Loop FMPLL PXN20 Microcontroller Reference Manual Rev 1 7 20 Freescale Semiconductor...
Страница 268: ...Boot Assist Module BAM PXN20 Microcontroller Reference Manual Rev 1 9 14 Freescale Semiconductor...
Страница 318: ...Interrupts and Interrupt Controller INTC PXN20 Microcontroller Reference Manual Rev 1 10 50 Freescale Semiconductor...
Страница 326: ...General Purpose Static RAM SRAM PXN20 Microcontroller Reference Manual Rev 1 11 8 Freescale Semiconductor...
Страница 372: ...e200z6 Core Z6 PXN20 Microcontroller Reference Manual Rev 1 13 8 Freescale Semiconductor...
Страница 412: ...e200z0 Core Z0 PXN20 Microcontroller Reference Manual Rev 1 14 14 Freescale Semiconductor...
Страница 460: ...Memory Protection Unit MPU PXN20 Microcontroller Reference Manual Rev 1 18 20 Freescale Semiconductor...
Страница 478: ...Error Correction Status Module ECSM PXN20 Microcontroller Reference Manual Rev 1 19 18 Freescale Semiconductor...
Страница 488: ...Software Watchdog Timer SWT PXN20 Microcontroller Reference Manual Rev 1 20 10 Freescale Semiconductor...
Страница 494: ...System Timer Module STM PXN20 Microcontroller Reference Manual Rev 1 21 6 Freescale Semiconductor...
Страница 821: ...Media Local Bus MLB PXN20 Microcontroller Reference Manual Rev 1 Freescale Semiconductor 27 49...
Страница 822: ...Media Local Bus MLB PXN20 Microcontroller Reference Manual Rev 1 27 50 Freescale Semiconductor...
Страница 926: ...Controller Area Network FlexCAN PXN20 Microcontroller Reference Manual Rev 1 29 42 Freescale Semiconductor...
Страница 990: ...Deserial Serial Peripheral Interface DSPI PXN20 Microcontroller Reference Manual Rev 1 30 64 Freescale Semiconductor...
Страница 1044: ...Enhanced Serial Communication Interface eSCI PXN20 Microcontroller Reference Manual Rev 1 31 54 Freescale Semiconductor...
Страница 1080: ...Cross Triggering Unit CTU PXN20 Microcontroller Reference Manual Rev 1 33 12 Freescale Semiconductor...
Страница 1134: ...Analog to Digital Converter ADC PXN20 Microcontroller Reference Manual Rev 1 34 54 Freescale Semiconductor...
Страница 1150: ...IEEE 1149 1 Test Access Port Controller JTAGC PXN20 Microcontroller Reference Manual Rev 1 35 16 Freescale Semiconductor...
Страница 1257: ...Nexus Development Interface NDI PXN20 Microcontroller Reference Manual Rev 1 Freescale Semiconductor 36 107...
Страница 1258: ...Nexus Development Interface NDI PXN20 Microcontroller Reference Manual Rev 1 36 108 Freescale Semiconductor...
Страница 1376: ...Memory Map PXN20 Microcontroller Reference Manual Rev 1 A 118 Freescale Semiconductor...