Regarding the 8 bit write to a 16 bit timer, the write is buffered
according to the datasheet until the low byte is written. (Not inc/Dec,
whole write) timer interval is longer than the interrupt.

On Tuesday, December 19, 2017, Brent Brown <brent@eds.co.nz> wrote:

> You're probably on to this already, and we haven't seen your code, but
> stopping the
> timer before writing to it will be important.
>
> Timer incrementing or decrementing in the midst of instructions accessing
> it messes
> things up, with the kind of irregularities you're seeing. Especially a
> problem with a
> 16 bit timer and 8 bit instruction.
>
--=20
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