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External timestamp value to set (in seconds, UTC+00).
Returned Values
DEF_OK, if External timestamp succesfully set;
DEF_FAIL, otherwise.
Required Configuration
Required callback function that must be implemented in your application if CLK_CFG_EXT_EN is DEF_ENABLED in clk_cfg.h (see section 3-1-1) in order for the clock/calendar to be maintained by an external clock/timestamp mechanism.
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