MC9S08AC60_11 Datasheet, PDF (170/350 Pages) Freescale Semiconductor, Inc – Microcontrollers

Internal Clock Generator (S08ICGV4)
10.2 External Signal Description
The oscillator pins are used to provide an external clock source for the MCU. The oscillator pins are gain
controlled in low-power mode (default). Oscillator amplitudes in low-power mode are limited to
approximately 1 V, peak-to-peak.
10.2.1 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.
10.2.2 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.
10.2.3 External Clock Connections
If an external clock is used, then the pins are connected as shown Figure 10-4.
ICG
EXTAL
V_SS
XTAL
NOT CONNECTED
CLOCK INPUT
Figure 10-4. External Clock Connections
10.2.4 External Crystal/Resonator Connections
If an external crystal/resonator frequency reference is used, then the pins are connected as shown in
Figure 10-5. Recommended component values are listed in the Electrical Characteristics chapter.
MC9S08AC60 Series Data Sheet, Rev. 3
170
Freescale Semiconductor