MCG_C4 field descriptionsField Description7DMX32DCO Maximum Frequency with 32.768 kHz ReferenceThe DMX32 bit controls whether the DCO frequency range is narrowed to its maximum frequency with a32.768 kHz reference.The following table identifies settings for the DCO frequency range.NOTE: The system clocks derived from this source should not exceed their specified maximums.DRST_DRS DMX32 Reference Range FLL Factor DCO Range00 0 31.25–39.0625 kHz 640 20–25 MHz1 32.768 kHz 732 24 MHz01 0 31.25–39.0625 kHz 1280 40–50 MHz1 32.768 kHz 1464 48 MHz10 0 31.25–39.0625 kHz 1920 60–75 MHz1 32.768 kHz 2197 72 MHz11 0 31.25–39.0625 kHz 2560 80–100 MHz1 32.768 kHz 2929 96 MHz0 DCO has a default range of 25%.1 DCO is fine-tuned for maximum frequency with 32.768 kHz reference.6–5DRST_DRSDCO Range SelectThe DRS bits select the frequency range for the FLL output, DCOOUT. When the LP bit is set, writes tothe DRS bits are ignored. The DRST read field indicates the current frequency range for DCOOUT. TheDRST field does not update immediately after a write to the DRS field due to internal synchronizationbetween clock domains. See the DCO Frequency Range table for more details.00 Encoding 0 — Low range (reset default).01 Encoding 1 — Mid range.10 Encoding 2 — Mid-high range.11 Encoding 3 — High range.4–1FCTRIMFast Internal Reference Clock Trim SettingFCTRIM 1 controls the fast internal reference clock frequency by controlling the fast internal referenceclock period. The FCTRIM bits are binary weighted, that is, bit 1 adjusts twice as much as bit 0. Increasingthe binary value increases the period, and decreasing the value decreases the period.If an FCTRIM[3:0] value stored in nonvolatile memory is to be used, it is your responsibility to copy thatvalue from the nonvolatile memory location to this register.0SCFTRIMSlow Internal Reference Clock Fine TrimSCFTRIM 2 controls the smallest adjustment of the slow internal reference clock frequency. SettingSCFTRIM increases the period and clearing SCFTRIM decreases the period by the smallest amountpossible.If an SCFTRIM value stored in nonvolatile memory is to be used, it is your responsibility to copy that valuefrom the nonvolatile memory location to this bit.1. A value for FCTRIM is loaded during reset from a factory programmed location .2. A value for SCFTRIM is loaded during reset from a factory programmed location .Chapter 24 Multipurpose Clock Generator (MCG)KL25 Sub-Family Reference Manual, Rev. 3, September 2012Freescale Semiconductor, Inc. 375
