
Clock Module
Freescale Semiconductor
7-9
this operation is known as non-dithered operation. The selection of dithered or non-dithered operation is
controlled by the PCR[DITHEN] bit. The percent frequency deviation and dither modulation frequency
are also controlled by the PCR and PMDR registers, whose operation is described in
“Dithering Waveform Definition.”
After reset, dithering is disabled. After the PLL has locked (indicated by the MISCCR[PLLLOCK] bit
described in
Section 9.3.4, “Miscellaneous Control Register (MISCCR)”
), the PLL may be changed from
non-dithered operation to dithered operation by writing to the PCR. After the PCR[DITHEN] bit has been
set, the PLL synchronizes the new value with the VCO clock domain. Then the transition from
non-dithered operation to dithered operation takes place such that the PLL output clocks remain
glitch-free. However, the dithering waveform and deviation percentages are not guaranteed to meet
specifications until two modulation periods have passed after the time of the write to the PCR register.
During the transition the frequency of the PLL output clocks does not exceed 10% of the respective
non-dithered frequency.
The PLL may also be changed from dithered operation to non-dithered operation by clearing the
PCR[DITHEN] bit. After this occurs, the PLL synchronizes the new value with the VCO clock domain.
Then, the transition from dithered operation to non-dithered operation takes place such that PLL output
clocks remain glitch-free. However, the frequency of the PLL output clocks are not guaranteed to be
completely stable until one modulation period has passed after the time of the write to the PCR. During
the transition the frequency of the PLL output clocks does not exceed 10% of the respective non-dithered
frequency.
Because the transition between dithered and non-dithered operation (and vice-versa) takes a period of time
to change, the PCR may not be written back-to-back without waiting two modulation periods between
writes.
NOTE
Failure to wait two modulation periods between writes to the PCR results in
unpredictable PLL operation.
7.3.2
Dithering Waveform Definition
The dithering waveform created by the changes in the frequency of the PLL output clocks is defined by
the percent frequency deviation and dither modulation frequency. The definitions of the percent frequency
deviation (or dithering deviation) and the modulation period (which is the inverse of the dither modulation
frequency) are shown in
. The dithering deviation is controlled by PCR[DITHDEV] field, while
the dither modulation frequency is controlled by the PMDR[MODDIV] field.
MCF5329 Reference Manual, Rev 3
Summary of Contents for MCF5329
Page 106: ...ColdFire Core 3 32 Freescale Semiconductor MCF5329 Reference Manual Rev 3...
Page 148: ...Cache 5 22 Freescale Semiconductor MCF5329 Reference Manual Rev 3...
Page 154: ...Static RAM SRAM 6 6 Freescale Semiconductor MCF5329 Reference Manual Rev 3...
Page 184: ...Power Management 8 18 Freescale Semiconductor MCF5329 Reference Manual Rev 3...
Page 204: ...Reset Controller Module 10 8 Freescale Semiconductor MCF5329 Reference Manual Rev 3...
Page 220: ...System Control Module SCM 11 16 Freescale Semiconductor MCF5329 Reference Manual Rev 3...
Page 228: ...Crossbar Switch XBS 12 8 Freescale Semiconductor MCF5329 Reference Manual Rev 3...
Page 268: ...General Purpose I O Module 13 40 Freescale Semiconductor MCF5329 Reference Manual Rev 3...
Page 392: ...SDRAM Controller SDRAMC 18 30 Freescale Semiconductor MCF5329 Reference Manual Rev 3...
Page 436: ...Fast Ethernet Controller FEC 19 44 Freescale Semiconductor MCF5329 Reference Manual Rev 3...
Page 594: ...FlexCAN 23 30 Freescale Semiconductor MCF5329 Reference Manual Rev 3...
Page 678: ...Pulse Width Modulation PWM Module 26 22 Freescale Semiconductor MCF5329 Reference Manual Rev 3...
Page 684: ...Watchdog Timer Module 27 6 Freescale Semiconductor MCF5329 Reference Manual Rev 3...
Page 704: ...DMA Timers DTIM0 DTIM3 29 12 Freescale Semiconductor MCF5329 Reference Manual Rev 3...
Page 754: ...UART Modules 31 34 Freescale Semiconductor MCF5329 Reference Manual Rev 3...
Page 770: ...I2 C Interface 32 16 Freescale Semiconductor MCF5329 Reference Manual Rev 3...
Page 866: ...Debug Module 36 50 Freescale Semiconductor MCF5329 Reference Manual Rev 3...