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Table 30-16. MCGOUTCLK Frequency Calculation Options
(continued)
Clock Mode
f
MCGOUTCLK
Note
FBI (FLL bypassed internal)
MCGIRCLK
Selectable between slow and fast
IRC
PEE (PLL engaged external)
(OSCCLK / PLL_R) × M / 2
OSCCLK / PLL_R must be in the
range of 8 – 16 MHz
PBE (PLL bypassed external)
OSCCLK
OSCCLK / PLL_R must be in the
range of 8 – 16 MHz
BLPI (Bypassed low power internal)
MCGIRCLK
Selectable between slow and fast
IRC
BLPE (Bypassed low power external)
OSCCLK
1. FLL_R is the reference divider selected by the C1[FRDIV] bits, F is the FLL factor selected by C4[DRST_DRS] and
C4[DMX32] bits , PLL_R is the reference divider selected by C5[PRDIV0] bits, and M is the multiplier selected by
C6[VDIV0] bits.
This section will include several mode switching examples, using an 16 MHz external
crystal. If using an external clock source less than 8 MHz, the MCG must not be
configured for any of the PLL modes (PEE and PBE).
30.5.3.1 Example 1: Moving from FEI to PEE Mode with OSC0 as the
source for the external crystal clock: External Crystal = 16
MHz, MCGOUTCLK frequency = 120 MHz
In this example, the MCG will move through the proper operational modes from FEI to
PEE to achieve 120 MHz MCGOUTCLK frequency from 16 MHz external crystal
reference. First, the code sequence will be described. Then there is a flowchart that
illustrates the sequence.
1. First, FEI must transition to FBE mode:
a. C2 = 0x2C
• C2[RANGE] set to 2'b10 because the frequency of 16 MHz is within the
high frequency range.
• C2[HGO] set to 1 to configure the crystal oscillator for high gain operation.
• C2[EREFS] set to 1, because a crystal is being used.
b. C1 = 0xA0
• C1[CLKS] set to 2'b10 to select external reference clock as system clock
source
Chapter 30 Multipurpose Clock Generator (MCG)
KV4x Reference Manual, Rev. 2, 02/2015
Freescale Semiconductor, Inc.
Preliminary
573
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