Information

MCG_C2 field descriptions (continued)
Field Description
Selects the source for the external reference clock. See the Oscillator (OSC) chapter for more details.
0 External reference clock requested.
1 Oscillator requested.
1
LP
Low Power Select
Controls whether the FLL or PLL is disabled in BLPI and BLPE modes. In FBE or PBE modes, setting this
bit to 1 will transition the MCG into BLPE mode; in FBI mode, setting this bit to 1 will transition the MCG
into BLPI mode. In any other MCG mode, LP bit has no affect.
0 FLL or PLL is not disabled in bypass modes.
1 FLL or PLL is disabled in bypass modes (lower power)
0
IRCS
Internal Reference Clock Select
Selects between the fast or slow internal reference clock source.
0 Slow internal reference clock selected.
1 Fast internal reference clock selected.
24.3.3 MCG Control 3 Register (MCG_C3)
Address: MCG_C3 is 4006_4000h base + 2h offset = 4006_4002h
Bit 7 6 5 4 3 2 1 0
Read
SCTRIM
Write
Reset
x* x* x* x* x* x* x* x*
* Notes:
x = Undefined at reset.•
MCG_C3 field descriptions
Field Description
7–0
SCTRIM
Slow Internal Reference Clock Trim Setting
SCTRIM
1
controls the slow internal reference clock frequency by controlling the slow internal reference
clock period. The SCTRIM bits are binary weighted, that is, bit 1 adjusts twice as much as bit 0.
Increasing the binary value increases the period, and decreasing the value decreases the period.
An additional fine trim bit is available in C4 register as the SCFTRIM bit. Upon reset, this value is loaded
with a factory trim value.
If an SCTRIM value stored in nonvolatile memory is to be used, it is your responsibility to copy that value
from the nonvolatile memory location to this register.
1. A value for SCTRIM is loaded during reset from a factory programmed location .
Memory Map/Register Definition
K20 Sub-Family Reference Manual, Rev. 2, Feb 2012
436 Freescale Semiconductor, Inc.