This depends on the operating system you are using. For Linux and Android, there are shell commands like “power off” or “shutdown” which will call several routines to store content and finally power down the system. One possibility for a power-down is to de-assert the PMIC_ON_REQ line. This will cause the PMIC to power down the rails according to the sequencing requirements. Such de-assertion can be achieved while writing to the SNVS_LPCR register, bit TOP and DP_EN, according to the NXP i.MX 8M/Mini/Nano Reference Manuals. For precise description of “power-down function” of the board support package including low-level driver, please contact the SoC manufacturer.