Information

NOTE
For the USB FS OTG controller to operate, the minimum
system clock frequency is 20 MHz.
The USB OTG controller also requires a 48 MHz clock. The clock source options are
shown below.
USB 48MHz
USB_CLKIN
MCGPLLCLK or
MCGFLLCLK
SIM_CLKDIV2
[USBFRAC, USBDIV]
SIM_SOPT2[USBSRC]
Figure 5-6. USB 48 MHz clock source
5.7.7 FlexCAN clocking
The clock for the FlexCAN's protocol engine can be selected as shown in the following
figure.
CANx_CTRL1[CLKSRC]
FlexCAN clock
Bus clock
OSCERCLK
Figure 5-7. FlexCAN clock generation
5.7.8 UART clocking
UART0 and UART1 modules operate from the core/system clock, which provides higher
performance level for these modules. All other UART modules operate from the bus
clock.
Chapter 5 Clock Distribution
K20 Sub-Family Reference Manual, Rev. 6, Nov 2011
Freescale Semiconductor, Inc. 177