T
Dougster said:How could such long period be implemented?
As 42Bastian Schick suggests - use software.
Have a timer configured to some suitable time interval - or "tick" - and then count the ticks to give the delay you require.
This is a general approach - not specific to Cortex-M; eg, it's how the Arduino millis() works ...
In fact, it's not even specific to microcontrollers - it's how mechanical clocks have worked for centuries!