• Writing a larger value slows down the ICSIRCLK frequency.
• Writing a smaller value to the ICSTRM register speeds up the ICSIRCLK frequency.
The TRIM bits affect the ICSOUT frequency if the ICS is in FLL engaged internal (FEI),
FLL bypassed internal (FBI), or FLL bypassed internal low power (FBILP) mode.
Until ICSIRCLK is trimmed, programming low reference divider (BDIV) factors may
result in ICSOUT frequencies that exceed the maximum chip-level frequency and violate
the chip-level clock timing specifications.
If ICS_C1[IREFSTEN] is set and the ICS_C1[IRCLKEN] bit is written to 1, the internal
reference clock keeps running during stop mode in order to provide a fast recovery upon
exiting stop.
All MCU devices are factory programmed with a trim value in a factory reserved
memory location (i.e. reserved nonvolatile information registers that can not be accessed
by users). This value is uploaded to the ICS_C3 register and ICS_C4 register during any
reset initialization. For finer precision, trim the internal oscillator in the application and
set the ICS_C4[SCFTRIM] bit accordingly.
NOTE
Some tools like ProcessorExpert or USB Multilink may use
flash memory location, such as 0xFF6F and/or 0xFF6E, to store
the temporary trim value.
8.2.1.4 Fixed frequency clock (ICSFFCLK)
The ICS presents the divided FLL reference clock as ICSFFCLK for use as an additional
clock source. ICSFFCLK frequency must be no more than 1/4 of the ICSOUT frequency
to be valid. When ICSFFCLK is valid, ICS output signal (ICSFFE) gets asserted high.
Because of this requirement, in bypass modes the ICSFFCLK is valid only in bypass
external modes (FBE and FBELP) for the following combinations of BDIV, RDIV, and
RANGE values:
• RANGE=1
• BDIV=000 (divide by 1), RDIV ≥ 010
• BDIV=001 (divide by 2), RDIV ≥ 011
• BDIV=010 (divide by 4), RDIV ≥ 100
• BDIV=011 (divide by 8), RDIV ≥ 101
Chapter 8 Clock management
MC9S08PA4 Reference Manual, Rev. 5, 08/2017
NXP Semiconductors
155
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 ...