MC9S08AW60 Datasheet, PDF (131/320 Pages) Freescale Semiconductor, Inc – Microcontrollers

Internal Clock Generator (S08ICGV4)
• Mode 2 — Self-clocked (SCM)
Default mode of operation that is entered immediately after reset. The ICG’s FLL is open loop and
the digitally controlled oscillator (DCO) is free running at a frequency set by the filter bits.
• Mode 3 — FLL engaged internal (FEI)
In this mode, the ICG’s FLL is used to create frequencies that are programmable multiples of the
internal reference clock.
— FLL engaged internal unlocked is a transition state that occurs while the FLL is attempting to
lock. The FLL DCO frequency is off target and the FLL is adjusting the DCO to match the
target frequency.
— FLL engaged internal locked is a state that occurs when the FLL detects that the DCO is locked
to a multiple of the internal reference.
• Mode 4 — FLL bypassed external (FBE)
In this mode, the ICG is configured to bypass the FLL and use an external clock as the clock source.
• Mode 5 — FLL engaged external (FEE)
The ICG’s FLL is used to generate frequencies that are programmable multiples of the external
clock reference.
— FLL engaged external unlocked is a transition state that occurs while the FLL is attempting to
lock. The FLL DCO frequency is off target and the FLL is adjusting the DCO to match the
target frequency.
— FLL engaged external locked is a state which occurs when the FLL detects that the DCO is
locked to a multiple of the internal reference.
8.2 External Signal Description
The oscillator pins are used to provide an external clock source for the MCU.
8.2.1 EXTAL — External Reference Clock / Oscillator Input
If upon the first write to ICGC1, either the FEE mode or FBE mode is selected, this pin functions as either
the external clock input or the input of the oscillator circuit as determined by REFS. If upon the first write
to ICGC1, either the FEI mode or SCM mode is selected, this pin is not used by the ICG.
8.2.2 XTAL — Oscillator Output
If upon the first write to ICGC1, either the FEE mode or FBE mode is selected, this pin functions as the
output of the oscillator circuit. If upon the first write to ICGC1, either the FEI mode or SCM mode is
selected, this pin is not used by the ICG. The oscillator is capable of being configured to provide a higher
amplitude output for improved noise immunity. This mode of operation is selected by HGO = 1.
8.2.3 External Clock Connections
If an external clock is used, then the pins are connected as shown Figure 8-4.
MC9S08AW60 Data Sheet, Rev.1.0
Freescale Semiconductor
131