Hi, I booting the m4 with followed: m4boot=fatload mmc 0:1 0x80800000 cortex_m4_bsp.bin;cp.l 0x80800000 0x007f8000 2048;mw.l 0x020d8000 0xa0480539;mw.l 0x020d8000 0xa0480529; The example, see below, only print a String. But while A9 is booting I only get undefined symbols I defined the uart_from_osz environment variable, in reason of https://community.nxp.com/thread/349097 m4mmcargs=uart_from_osc clk_ignore_unused cpuidle.off=1 and now I got after completed boot the correct string. But why not after booting the m4? And why I get the login directive from the A9 on this UART too? I activate the UART2 over the DeviceTreeConfigurator and the uart ist also defined in the example.