S9S08SG8E2MTJ Datasheet, PDF (151/320 Pages) Freescale Semiconductor, Inc – MC9S08SG8 MC9S08SG4 Data Sheet Addendum

Chapter 10 
Internal Clock Source (S08ICSV2)
10.1 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 either an internal or an external
reference clock. The module can provide this FLL clock or either of the internal or external reference
clocks as a source for the MCU system clock. There are also signals provided to control a low power
oscillator (XOSC) module to allow the use of an external crystal/resonator as the external reference clock.
Whichever clock source is chosen, it is passed through a reduced bus divider (BDIV) which allows a lower
final output clock frequency to be derived.
The bus frequency will be one-half of the ICSOUT frequency.
NOTE
For MC9S08SG8, it is 1.5% deviation for -40 °C to 125 °C
standard-temperature rated devices and 3% deviation for AEC Grade 0
high-temperature rated devices (-40 to 150 °C).
10.1.1 Module Configuration
When the internal reference is enabled in stop mode (IREFSTEN = 1), the voltage regulator must also be
enabled in stop mode by setting the LVDE and LVDSE bits in the SPMSC1 register.
Figure 10-1 shows the MC9S08SG8 block diagram with the ICS module highlighted.
MC9S08SG8 MCU Series Data Sheet, Rev. 7
Freescale Semiconductor
147