TM4C123GE6PZ Datasheet, PDF (221/1445 Pages) Texas Instruments – Tiva™ TM4C123GE6PZ Microcontroller

Tiva^™ TM4C123GE6PZ Microcontroller
■ Crystal input selection
Important: Write the RCC register prior to writing the RCC2 register.
When transitioning the system clock configuration to use the MOSC as the fundamental
clock source, the MOSCDIS bit must be set prior to reselecting the MOSC or an undefined
system clock configuration can sporadically occur.
The configuration of the system clock must not be changed while an EEPROM operation
is in process. Software must wait until the WORKING bit in the EEPROM Done Status
(EEDONE) register is clear before making any changes to the system clock.
Figure 5-5 shows the logic for the main clock tree. The peripheral blocks are driven by the system
clock signal and can be individually enabled/disabled. The ADC clock signal can be selected from
the PIOSC, the system clock if the PLL is disabled, or the PLL output divided down to 16 MHz if the
PLL is enabled. The PWM clock signal is a synchronous divide of the system clock to provide the
PWM circuit with more range (set with PWMDIV in RCC).
Note: If the ADC module is not using the PIOSC as the clock source, the system clock must be
at least 16 MHz. When the USB module is in operation, MOSC must be the clock source,
either with or without using the PLL, and the system clock must be at least 20 MHz.
June 12, 2014
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