MC9RS08KA1 FREESCALE [Freescale Semiconductor, Inc], MC9RS08KA1 Datasheet - Page 74

• Manufacturer Part Number: MC9RS08KA1
• Description: RS08 Microcontrollers
• Manufacturer: FREESCALE [Freescale Semiconductor, Inc]

Chapter 9 Internal Clock Source (RS08ICSV1)
9.2
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 an internal reference clock. The
module can provide this FLL clock or the internal reference clock as a source for the MCU system clock,
ICSOUT.
Whichever clock source is chosen, ICSOUT is passed through a bus clock divider (BDIV) which allows a
lower final output clock frequency to be derived. ICSOUT is two times the bus frequency.
9.2.1
Key features of the ICS module are:
9.2.2
There are four modes of operation for the ICS: FEI, FBI, FBILP, and stop.
9.2.2.1
In FLL engaged internal mode, which is the default mode, the ICS supplies a clock derived from the FLL
which is controlled by the internal reference clock.
9.2.2.2
In FLL bypassed internal mode, the FLL is enabled and controlled by the internal reference clock, but is
bypassed. The ICS supplies a clock derived from the internal reference clock.
9.2.2.3
In FLL bypassed internal low power mode, the FLL is disabled and bypassed, and the ICS supplies a clock
derived from the internal reference clock.
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Frequency-locked loop (FLL) is trimmable for accuracy
— 0.2% resolution using internal 32 kHz reference
— 2% deviation over voltage and temperature using internal 32 kHz reference
— DCO output is 512 times internal reference frequency
Internal reference clock has 9 trim bits available
Internal reference clock 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, and 8)
FLL engaged internal mode is automatically selected out of reset
Introduction
Features
Modes of Operation
FLL Engaged Interna
FLL Bypassed Interna
FLL Bypassed Interna
MC9RS08KA2 Series Data Sheet, Rev. 3
l (FEI)
l (FBI)
l Low Power (FBILP)
Freescale Semiconductor