2
/
/
2
n
2
n
IREFSTEN
IREFSTEN
ICSIRCLK
ICSOUT
ICSLCLK
Internal Clock Source Block
ICSFFCLK
DCOOUT
Filter
FLL
Internal
Reference
Clock
n=0-7
n=0-7
SCFTRIMSCTRIM
IREFST
CLKST
IRCLKEN
DCO
LP
CLKS
BDIV
RDIV
IREFS
LOLIE
LOLS
LOCK
CME
External Reference Clock /
Oscillator
ICSBDCCLK
CLKSW
BUSCLK
Figure 8-2. Internal clock source (ICS)
8.2.1.1 Bus frequency divider
The ICS_C2[BDIV] bits can be changed at anytime and the actual switch to the new
frequency occurs immediately.
8.2.1.2 Low power bit usage
The low power bit (ICS_C2[LP]) is provided to allow the FLL to be disabled and thus
conserve power when it is not used.
However, in some applications it may be desirable to allow the FLL to be enabled and to
lock for maximum accuracy before switching to an FLL engaged mode. To do this, write
the ICS_C2[LP] bit to 0.
8.2.1.3 Internal reference clock (ICSIRCLK)
When ICS_C1[IRCLKEN] is set the internal reference clock signal is presented as
ICSIRCLK, which can be used as an additional clock source. To re-target the ICSIRCLK
frequency, write a new value to the ICS_C3[SCTRIM] and ICS_C4[SCFTRIM] bits to
trim the period of the internal reference clock:
Internal clock source (ICS)
MC9S08PA4 Reference Manual, Rev. 5, 08/2017
154
NXP Semiconductors
Summary of Contents for MC9S08PA4
Page 1: ...MC9S08PA4 Reference Manual Supports MC9S08PA4 Document Number MC9S08PA4RM Rev 5 08 2017 ...
Page 2: ...MC9S08PA4 Reference Manual Rev 5 08 2017 2 NXP Semiconductors ...
Page 22: ...MC9S08PA4 Reference Manual Rev 5 08 2017 22 NXP Semiconductors ...
Page 28: ...System clock distribution MC9S08PA4 Reference Manual Rev 5 08 2017 28 NXP Semiconductors ...
Page 150: ...Port data registers MC9S08PA4 Reference Manual Rev 5 08 2017 150 NXP Semiconductors ...
Page 196: ...Human machine interfaces HMI MC9S08PA4 Reference Manual Rev 5 08 2017 196 NXP Semiconductors ...
Page 224: ...Instruction Set Summary MC9S08PA4 Reference Manual Rev 5 08 2017 224 NXP Semiconductors ...
Page 232: ...Functional Description MC9S08PA4 Reference Manual Rev 5 08 2017 232 NXP Semiconductors ...
Page 258: ...FTM Interrupts MC9S08PA4 Reference Manual Rev 5 08 2017 258 NXP Semiconductors ...
Page 294: ...Functional description MC9S08PA4 Reference Manual Rev 5 08 2017 294 NXP Semiconductors ...
Page 398: ...Resets MC9S08PA4 Reference Manual Rev 5 08 2017 398 NXP Semiconductors ...
Page 400: ...MC9S08PA4 Reference Manual Rev 5 08 2017 400 NXP Semiconductors ...