CLOCK_XMC4: Overview




The CLOCK_XMC4 APP provides the following functionalities:

  1. Setting the sources of various clocks in xmc4 devices.
  2. Calibration selection for internal fast oscillator settings.
  3. Configuration of Main / System PLL settings.
  4. Conditional configuration of external clock output settings, to monitor a various clocks: System Clock, Main PLL clock, USB PLL clock, Standby clock (only for xmc42/41 devices).
  5. Setting the entire clock setup using SystemCoreClockSetup().
  6. Runtime clock changes are supported.


  1. By default, the SystemInit() calls weak API SystemCoreClockSetup() which exits in system_XMC4x.c file. When the CLOCK_XMC4 APP used in the project, then SystemInit() calls the SystemCoreClockSetup() which exists in clock_xmc4_conf.c file.
Figure 1 : Hardware and Software connectivity of CLOCK_XMC4 APP

Figure 1, shows how the APP is structured in DAVEā„¢. The CLOCK_XMC4 APP uses SCU module to generate a various clocks such as: System clock, peripheral clock backup clock, Standby clock etc. And it also uses GPIO module to monitor an external clock output.

Figure 2 : Clock selection & generation unit

Figure 2, shows how the various clocks are derived from the source.


  1. For XMC42/1 devices, the maximum PLL clock and system clock frequency are limited to 80MHz.
  2. The clock generated for the various unit of device may differ based on other XMC4x derivatives.
  3. Additionally the APP is checking for appropriate clock ratio combinations between fCCU, fCPU and fPERIPH. The valid values of clock divide registers for fCCU, fCPU and fPERIPH clocks are mentioned below
    Figure 3 : Valid clock ratio combinations between fCCU, fCPU and fPERIPH

Supported Devices

The APP supports below devices:

  1. XMC4800 Series
  2. XMC4700 Series
  3. XMC4500 Series
  4. XMC4400 Series
  5. XMC4300 Series
  6. XMC4200 / XMC4100 Series


  1. XMC4800 Reference Manual
  2. XMC4700 Reference Manual
  3. XMC4500 Reference Manual
  4. XMC4400 Reference Manual
  5. XMC4300 Reference Manual
  6. XMC4200 Reference Manual
  7. XMC4100 Reference Manual