MPC5553/MPC5554 Microcontroller Reference Manual, Rev. 5
11-28
Freescale Semiconductor
— Write FMPLL_SYNCR[PREDIV] for the desired final value.
— Write FMPLL_SYNCR[MFD] for the desired final value.
— Write FMPLL_SYNCR[EXP] for the desired final value.
— Write FMPLL_SYNCR[RATE] for the desired final value.
— Write the RFD control field for 1 + the desired final RFD value (RFD must be programmed to
be >1 to protect from overshoot).
2. Wait for the FMPLL to lock by monitoring the FMPLL_SYNSR[LOCK] bit. Refer to
Section 11.3.1.1, “Synthesizer Control Register (FMPLL_SYNCR)
,” for memory
synchronization between changing FMPLL_SYNCR[MFD] and monitoring the lock status.
3. If using the frequency modulation feature, then:
a) Enable FM by setting FMPLL_SYNCR[DEPTH] =1 or 2.
b) Also set FMPLL_SYNCR[RATE] if not done previously in step 2.
4. Calibration starts. After calibration is done, then the FMPLL will re-lock. Wait for the FMPLL to
re-lock by monitoring the FMPLL_SYNSR[LOCK] bit.
5. Verify FM calibration completed and was successful by testing the
FMPLL_SYNSR[CALDONE] and FMPLL_SYNSR[CALPASS] bitfields.
6. If FM calibration did not complete or was not successful, attempt again by going back to step 1.
7. Initialize the FMPLL for the desired final frequency by changing FMPLL_SYNCR[RFD] to its
desired final value.Note that the FMPLL will not need to re-lock when only changing the RFD.
8. Re-enable LOLIRQ.
NOTE
This first register write will cause the FMPLL to switch to an initial
frequency which is less than the final one. Keeping the change of frequency
to a lower initial value helps minimize the current surge to the external
power supply caused by change of frequency. The last step will be to only
change the RFD to get to the desired final frequency.
NOTE
Changing the MFD or PREDIV values causes the FMPLL to perform a
search for the lock frequency that results in the system clock frequency
changing rapidly across the complete frequency range. All MCU
peripherals, including the external bus will be subjected to this frequency
sweep. Operation of timers and serial communications during this search
sequence will produce unpredictable results.
Note that the frequency modulation system is dependent upon several factors: the accuracies of the
V
DDSYN
/V
SSSYN
voltage, of the crystal oscillator frequency, and of the manufacturing variation.
For example, if a 5% accurate supply voltage is utilized, then a 5% modulation depth error will result. If
the crystal oscillator frequency is skewed from 8 MHz the resulting modulation frequency will be
proportionally skewed. Finally, the error due to the manufacturing and environment variation alone can
cause the frequency modulation depth error to be greater than 20%.
Summary of Contents for MPC5553
Page 5: ...MPC5553 MPC5554 Microcontroller Reference Manual Rev 5 2 Freescale Semiconductor...
Page 21: ...MPC5553 MPC5554 Microcontroller Reference Manual Rev 5 xvi Freescale Semiconductor...
Page 47: ...MPC5553 MPC5554 Microcontroller Reference Manual Rev 5 1 26 Freescale Semiconductor...
Page 163: ...MPC5553 MPC5554 Microcontroller Reference Manual Rev 5 4 20 Freescale Semiconductor...
Page 179: ...MPC5553 MPC5554 Microcontroller Reference Manual Rev 5 5 16 Freescale Semiconductor...
Page 561: ...MPC5553 MPC5554 Microcontroller Reference Manual Rev 5 13 38 Freescale Semiconductor...
Page 615: ...MPC5553 MPC5554 Microcontroller Reference Manual Rev 5 14 54 Freescale Semiconductor...
Page 707: ...MPC5553 MPC5554 Microcontroller Reference Manual Rev 5 17 68 Freescale Semiconductor...
Page 755: ...MPC5553 MPC5554 Microcontroller Reference Manual Rev 5 18 48 Freescale Semiconductor...
Page 873: ...MPC5553 MPC5554 Microcontroller Reference Manual Rev 5 19 118 Freescale Semiconductor...
Page 984: ...MPC5553 MPC5554 Microcontroller Reference Manual Rev 5 Freescale Semiconductor 21 41...
Page 985: ...MPC5553 MPC5554 Microcontroller Reference Manual Rev 5 21 42 Freescale Semiconductor...
Page 1019: ...MPC5553 MPC5554 Microcontroller Reference Manual Rev 5 22 34 Freescale Semiconductor...
Page 1129: ...MPC5553 MPC5554 Microcontroller Reference Manual Rev 5 25 90 Freescale Semiconductor...