MPC5553/MPC5554 Microcontroller Reference Manual, Rev. 5
11-16
Freescale Semiconductor
11.3.1.2
Synthesizer Status Register (FMPLL_SYNSR)
The synthesizer status register (FMPLL_SYNSR) is a 32-bit register. Only the LOLF and LOCF flag bits
are writable in this register. Writes to bits other than the LOLF and LOCF have no effect.
19
RATE
Modulation rate. Controls the rate of frequency modulation applied to the system
frequency. The allowable modulation rates are shown below. Changing the rate by writing
to the RATE bit initiates the FM calibration sequence.
Note: To avoid unintentional interrupt requests, clear LOLIRQ before changing RATE.
Note: F
mod
must be between 100 MHz and 250 MHz. Refer to
“Programming System Clock Frequency with Frequency Modulation
.”
20–21
DEPTH
[0:1]
Controls the frequency modulation depth and enables the frequency modulation. When
programmed to a value other than 0x0, the frequency modulation is automatically enabled.
The programmable frequency deviations from the system frequency are shown below.
Upon a change in the depth value to other than 0x0, the calibration sequence will be
reinitialized.
Note: To avoid unintentional interrupt requests, clear LOLIRQ before changing DEPTH.
22–31
EXP
[0:9]
Expected difference value. Holds the expected value of the difference of the reference and
the feedback counters. See
Section 11.4.3.3, “FM Calibration Routine
” to determine the
value of these bits. This field is written by the application before entering calibration mode.
Table 11-5. FMPLL_SYNCR Field Descriptions (Continued)
Bits
Name
Description
RATE
Modulation Rate (Hz)
0
F
mod
= F
ref_crystal
/ (1 ) 80
F
mod
= F
ref_ext
/ (1 ) 80
1
F
mod
= F
ref_crystal
/ (1 ) 40
F
mod
= F
ref_ext
/ (1 ) 40
DEPTH[1]
DEPTH[0]
Modulation Depth (% of Fsys)
0
0
0
0
1
1.0
0.2
1
0
2.0
0.2
1
1
Reserved
Summary of Contents for MPC5553
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