MC9S08QD4_07 Datasheet, PDF (123/202 Pages) Freescale Semiconductor, Inc – 8-Bit HCS08 Central Processor Unit (CPU)

Chapter 9
Internal Clock Source (S08ICSV1)
9.1 Introduction
The internal clock source (ICS) module provides clock source choices for the MCU. The module contains
a frequency-locked loop (FLL) as a clock source that is controllable by an internal reference clock. The
module can provide this FLL clock or the internal reference clock as a source for the MCU system clock,
ICSOUT.
Whichever clock source is chosen, ICSOUT is passed through a bus clock divider (BDIV) which allows a
lower final output clock frequency to be derived. ICSOUT is two times the bus frequency.
Figure 9-1 Shows the MC9S08QD4 series with the ICS module highlighted.
9.1.1 ICS Configuration Information
Bit-1 and bit-2 of ICS control register 1 (ICSC1) always read as 1.
MC9S08QD4 Series MCU Data Sheet, Rev. 3
Freescale Semiconductor
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