[En-Nut-Discussion] NutGetMillis overflow documentation

[Ole Reinhardt]

Hi!

> Normally you do timespan calculations that look like this:
> 
> if( now-past < span) { wait a bit }
> 
> These type of call will result in a jitter with every overflow.

That's not correct. As long as now and past are both uint32_t this
calculation will work correctly even if there was an overflow between
past and now. That's a nice effect of unsigned calculations :)

Example (8 bit)

Now = 10   = 0x0A
Past = 245 = 0xF5

now - past = 0x(ffffff)15 => truncated to 8 Bit = 0x15 = 21 (which is
totaly correct)

Regards,

Ole 

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