MC9S08GB60A Datasheet, PDF (107/302 Pages) Freescale Semiconductor, Inc – HCS08 Microcontrollers

Internal Clock Generator (S08ICGV2)
7.1.2 Modes of Operation
This is a high-level description only. Detailed descriptions of operating modes are contained in
Section 7.3, “Functional Description.”
• Mode 1 — Off
The output clock, ICGOUT, is static. This mode may be entered when the STOP instruction is
executed.
• Mode 2 — Self-clocked (SCM)
Default mode of operation that is entered out of 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 which 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 which 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 which 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.
7.2 Oscillator Pins
The oscillator pins are used to provide an external clock source for the MCU.
7.2.1 EXTAL— External Reference Clock / Oscillator Input
If upon the first write to ICGC1, either 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 FEI mode or SCM mode is selected, this pin is not used by the ICG.
7.2.2 XTAL— Oscillator Output
If upon the first write to ICGC1, either 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 FEI mode or SCM mode is selected, this
MC9S08GB60A Data Sheet, Rev. 2
Freescale Semiconductor
107