Re: [avr-libc-dev] [bug #30363] _delay_xx() functions in <util/delay.h> are broken

[Bob Paddock]

> The other issue that comes into play is rounding itself.
> For example, there are 3 ways to round cycles.
> - up (delay is always *at least* as long as requested)
> - down (delay is closest as possible without going over but can be worst
> case
> nearly 1 cycle shorter than requested)
> - closest (picks closest cycle which could round up or down)
>

In all of the places that I've used delays, I'd always want them to error on
the side of being a cycle to long, than any amount of to short.

Just for completeness, here is a summary of rounding methods:

http://www.pldesignline.com/showArticle.jhtml?articleID=189600747

    * Round-Toward-Nearest
    * Round-Half-Up (Arithmetic Rounding)
    * Round-Half-Down
    * Round-Half-Even (Banker's Rounding)
    * Round-Half-Odd
    * Round-Ceiling (Positive Infinity)
    * Round-Floor (Negative Infinity)
    * Round-Toward-Zero
    * Round-Away From-Zero
    * Round-Up
    * Round-Down
    * Truncation (Chopping)
    * Round-Alternate
    * Round-Random (Stochastic Rounding)
    * Sign-Magnitude Binary Values
    * Rounding Signed Binary Values

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