mcf51jf128 Freescale Semiconductor, Inc, mcf51jf128 Datasheet - Page 431

• Manufacturer Part Number: mcf51jf128
• Description: Mcf51jf128 Reference Manual
• Manufacturer: Freescale Semiconductor, Inc

Chapter 20
Multipurpose Clock Generator (MCG)
20.1 Introduction
The multipurpose clock generator (MCG) module provides several clock source choices
for the MCU. The module contains a frequency-locked loop (FLL) and a phase-locked
loop (PLL). The FLL is controllable by either an internal or an external reference clock.
The PLL is controllable by the external reference clock. The module can select either of
the FLL or PLL output clocks, or either of the internal or external reference clocks as a
source for the MCU system clock. The MCG operates in conjuction with a crystal
oscillator, which allows an external crystal, ceramic resonator, or another external clock
source to produce the external reference clock.
20.1.1 Features
Key features of the MCG module are:
Freescale Semiconductor, Inc.
• Frequency-locked loop (FLL)
• Phase-locked loop (PLL)
• Digitally-controlled oscillator (DCO)
• DCO frequency range is programmable for up to four different frequency ranges.
• Option to program and maximize DCO output frequency for a low frequency
• Option to prevent FLL from resetting its current locked frequency when
• Internal or external reference clock can be used as the FLL source.
• Can be used as a clock source for other on-chip peripherals.
external reference clock source.
switching clock modes if FLL reference frequency is not changed.
MCF51JF128 Reference Manual, Rev. 2, 03/2011
Preliminary
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