AnsweredAssumed Answered

LPC55S69 PLL1 does not function

Question asked by Rory Hand on May 10, 2020
Latest reply on May 26, 2020 by ZhangJennie




I am trying to use the inbuilt Clocks tool within MCUXpresso to configure the clocks for the FROHF96 functional group, for the LPC55S69EVK board.  I want to use PLL1 with the SD card, so I can run this block at 50MHz (as opposed to using the FROHF96MHz clock, which will only allow me a maximum speed of 48MHz).   I do not want to use PLL0 as this is already tied up running an I2S dma block.


If I configure PLL0 in the clocks tool, to use the XTAL32M clock running at 16MHz, and multiply and divide this to produce a 150MHz output, and then feed this to the SDIO block, and divide it by 3 to generate a 50MHz clock on the SDIO input, this configuration works.


If, however, I configure the PLL1 block in EXACTLY the same way, connect THIS to the SDIO block, and update the code accordingly, the frequency I read back from the sd block is 0Hz, and the sd card no longer properly functions.   (See photo below for set-up within the MCUXpresso clocks tool).



Additionally, I cannot set up the multiplier of either PLL exactly how I would like for other purposes; if for example, I wanted to boost the sdio speed to 52MHz, I would need to activate the 1MHz FRO, connect this to whichever PLL, and then multiply by 52 in the PLL...however, whenever I try changing this multiplier number to 52, the software crashes.


Any help much appreciated.