FSMC bus (External RAM) clocked by intenal crystal +PLL doesnt works.

[elharrar]

Posted on February 06, 2012 at 08:17

Hi all,

I have a problem with external RAM on FSMC bus (AHB3). If I use the external crystal the memory works well (12 Mhz + PLL to 96Mhz ), but if I use the internal crystal at 16Mhz + PLL to 96Mhz I stay blocked in     while((RCC->CR & RCC_CR_PLLRDY) == 0)     {     } in system_stm32f4xx.c or go to HardFault interrupt... Is there a known limitation AHB3/Internal crystal ? Thanks Mikael  [ small update ] An other update: When using standalone project (EWARM + external crystal + PLL at 96Mhz) all is OK but when using the same config with FreeRTOS , the init crash and go to HandlerException... an idea ?

[Tesla DeLorean]

Posted on February 06, 2012 at 17:10

Then you probably have the wrong multipliers on the PLL, causing it to clock beyond spec, and thus fail to lock.

Check that the IDE is using the right clock value for the internal RC (not a crystal). For random crashing, consider if the FLASH unit is properly initialized with suitable wait states.