11.1.3
Features
Key features of the ICS module are:
•
Frequency-locked loop (FLL) is trimmable for accuracy
•
Internal or external reference clocks can be used to control the FLL
•
Reference divider is provided for external clock
•
Internal reference clock has 9 trim bits available
•
Internal or external reference clocks can be selected as the clock source for the MCU
•
Whichever clock is selected as the source can be divided down
— 2 bit select for clock divider is provided
– Allowable dividers are: 1, 2, 4, 8
•
Control signals for a low power oscillator as the external reference clock are provided
— HGO, RANGE, EREFS, ERCLKEN, EREFSTEN
•
FLL Engaged Internal mode is automatically selected out of reset
•
BDC clock is provided as a constant divide by 2 of the low range DCO output
•
Three selectable digitally controlled oscillators (DCO) optimized for different frequency ranges.
•
Option to maximize output frequency for a 32768 Hz external reference clock source.
11.1.4
Block Diagram
Figure 11-2
is the ICS block diagram.
Freescale Semiconductor
MC9S08QE128 MCU Series Reference Manual, Rev. 2
Internal Clock Source (S08ICSV3)
205