![Freescale Semiconductor PXR4030 Скачать руководство пользователя страница 176](http://html1.mh-extra.com/html/freescale-semiconductor/pxr4030/pxr4030_reference-manual_2330660176.webp)
Frequency Modulated Phase-Locked Loop (FMPLL)
6-18
Freescale Semiconductor
PXR40 Microcontroller Reference Manual, Rev. 1
force the PLL to continually update and prevent a frequency drift phenomena referred to as
“dead-banding.” Dead-band describes the minimum amount of phase error between the reference and
feedback clocks that a phase detector cannot correct.
6.4.3.3.2
Charge Pump/Loop Filter
Operation of the charge pump is controlled by the UP and DOWN signals from the PFD. They control
whether the charge pumps apply or remove charge, respectively, from the loop filter.
6.4.3.3.3
VCO
The voltage into the VCO controls the frequency of its output. The frequency-to-voltage relationship
(VCO gain) is positive.
6.4.3.3.4
EMFD
The MFD divides down the output of the VCO and feeds it back to the PFD. The PFD controls the VCO
frequency (via the charge pump and loop filter) such that the reference and feedback clocks have the same
frequency and phase. Thus, the input to the MFD, which is also the output of the VCO, is at a frequency
that is the reference frequency multiplied by the same amount the MFD divides by. For example, if the
MFD divides the VCO frequency by 48, then the PLL is frequency locked when the VCO frequency is 48
times the reference frequency. The presence of the MFD in the loop allows the PLL to perform frequency
multiplication, or synthesis.
6.4.3.3.5
Programming System Clock Frequency
In normal PLL clock mode, the default system frequency is determined by the default EPREDIV, EMFD,
and ERFD values.
When programming the PLL, do not violate the maximum system clock frequency or max/min VCO
frequency specifications. Based on the desired system clock frequency, EPREDIV, EMFD, and ERFD
must be calculated for the given crystal or external reference frequency. See
PXR40 Microcontroller Data
Sheet
for the max/min VCO frequency range and the maximum allowable system frequency.
Frequency modulation should be disabled prior to changing the EPREDIV, EMFD, or ERATE bit fields.
A change to EPREDIV, EMFD, EDEPTH, or ERATE while modulation is enabled invalidates the previous
FM depth configuration.
Use these directions to accommodate the frequency overshoot that occurs when the EPREDIV or EMFD
bits are changed. If frequency modulation is going to be enabled the maximum allowable frequency must
be reduced by the programmed
F
m
.
1. Determine the appropriate value for the EPREDIV, EMFD, and ERFD fields in the synthesizer
control register(s), remember to include the
F
m
if frequency modulation is to be enabled. The
amount of jitter in the system clocks can be minimized by selecting the maximum EMFD factor
that can be paired with an ERFD factor to provide the desired frequency. The maximum EMFD
value that can be used is determined by the VCO and EMFD range.
Содержание PXR4030
Страница 1: ...PXR40 Microcontroller Reference Manual Devices Supported PXR4030 PXR4040 PXR40RM Rev 1 06 2011...
Страница 30: ...PXR40 Microcontroller Reference Manual Rev 1 Freescale Semiconductor xxx...
Страница 40: ...PXR40 Microcontroller Reference Manual Rev 1 xl Freescale Semiconductor...
Страница 66: ...Memory Map PXR40 Microcontroller Reference Manual Rev 1 2 4 Freescale Semiconductor...
Страница 120: ...Signal Descriptions 3 54 Freescale Semiconductor PXR40 Microcontroller Reference Manual Rev 1...
Страница 158: ...Power Management Controller PMC 5 26 Freescale Semiconductor PXR40 Microcontroller Reference Manual Rev 1...
Страница 182: ...Frequency Modulated Phase Locked Loop FMPLL 6 24 Freescale Semiconductor PXR40 Microcontroller Reference Manual Rev 1...
Страница 278: ...System Integration Unit SIU 7 96 Freescale Semiconductor PXR40 Microcontroller Reference Manual Rev 1...
Страница 280: ...System Information Module PXR40 Microcontroller Reference Manual Rev 1 8 2 Freescale Semiconductor...
Страница 300: ...Boot Assist Module BAM 9 20 Freescale Semiconductor PXR40 Microcontroller Reference Manual Rev 1...
Страница 346: ...Interrupts and Interrupt Controller INTC 10 46 Freescale Semiconductor PXR40 Microcontroller Reference Manual Rev 1...
Страница 352: ...General Purpose Static RAM SRAM 11 6 Freescale Semiconductor PXR40 Microcontroller Reference Manual Rev 1...
Страница 432: ...Core e200z7 Overview PXR40 Microcontroller Reference Manual Rev 1 13 44 Freescale Semiconductor...
Страница 460: ...Peripheral Bridge PBRIDGE 15 16 Freescale Semiconductor PXR40 Microcontroller Reference Manual Rev 1...
Страница 478: ...Memory Protection Unit MPU 16 18 Freescale Semiconductor PXR40 Microcontroller Reference Manual Rev 1...
Страница 496: ...Error Correction Status Module ECSM 17 18 Freescale Semiconductor PXR40 Microcontroller Reference Manual Rev 1...
Страница 524: ...Periodic Interrupt Timer PIT_RTI 20 12 Freescale Semiconductor PXR40 Microcontroller Reference Manual Rev 1...
Страница 740: ...FlexRay Communication Controller FLEXRAY 22 156 Freescale Semiconductor PXR40 Microcontroller Reference Manual Rev 1...
Страница 860: ...FlexCAN Module 24 50 Freescale Semiconductor PXR40 Microcontroller Reference Manual Rev 1...
Страница 928: ...Deserial Serial Peripheral Interface DSPI 25 68 Freescale Semiconductor PXR40 Microcontroller Reference Manual Rev 1...
Страница 982: ...Enhanced Serial Communication Interface eSCI 26 54 Freescale Semiconductor PXR40 Microcontroller Reference Manual Rev 1...
Страница 1114: ...Enhanced Queued Analog to Digital Converter EQADC 27 132 Freescale Semiconductor PXR40 Microcontroller Reference Manual Rev 1...
Страница 1167: ...Decimation Filter Freescale Semiconductor 28 53 PXR40 Microcontroller Reference Manual Rev 1...
Страница 1168: ...Decimation Filter 28 54 Freescale Semiconductor PXR40 Microcontroller Reference Manual Rev 1...
Страница 1262: ...Enhanced Time Processing Unit eTPU2 29 94 Freescale Semiconductor PXR40 Microcontroller Reference Manual Rev 1...
Страница 1399: ...Nexus Development Interface NDI Freescale Semiconductor 31 83 PXR40 Microcontroller Reference Manual Rev 1...
Страница 1400: ...Nexus Development Interface NDI 31 84 Freescale Semiconductor PXR40 Microcontroller Reference Manual Rev 1...