uint32 u32TickCount_ms

This is the ms timestamp since system startup.

Remark
The timestamp is updated in the TickTimer cycle (in the hardware interrupt handler). For example, if the TickTimer period [ms] is 4 ms, the timestamp will also be counted up by 4.
If the maximum count value is exceeded, the value returns to 0.
By calculating {past timestamp} - {current timestamp} you can calculate the time elapsed since the past (not exceeding the maximum count).
The starting value on return from sleep is indefinite. Please do not quote a value saved before sleep and do not process it after sleep.