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LPC54608 Powerlib/User manual UM10912

Question asked by Joachim Beck on Nov 21, 2017
Latest reply on Nov 23, 2017 by Joachim Beck



in the user manual UM10912 in chapter 6 page 120 the following can be found:


Use the PLL to boost the input frequency if a main clock is needed with a frequency higher than the FRO 12
MHz clock and the FRO 96 MHz or 48 MHz clock (fro_hf) is not appropriate. Before connecting the output
of the system PLL to the main clock, the user must call the POWER_SetVoltageForFreq API in SDK
software package to deliver the amount of power needed for the CPU operating frequency. The API call
sets the FLASHCFG register. See Chapter 8 “LPC546xx Power profiles/Power control API”. At 220 MHz
the system clock/access time can be lower when compared to 180 MHz because the power library
optimizes the on-chip voltage regulator.


I use Keil and copied the keil_lib_power.lib from the actual SDK_2.3.0_LPCXpresso64608. If i call the function 

POWER_SetVoltageForFreq (for example with frequency 96000000Hz) the register FLASHCFG is not changed by the function as stated in the manual (checked with the debugger).

If I do not change FLASHCFG manually together with the call of POWER_SetVoltageForFreq, my application crashes after switching the main clock to FROHF. If i manually set the FLASHCFG.FLASHTIM  everything seems to work. 


Is this a bug in the library or a documentation problem in UM10912?


Thank you for your support.