[sv-bc] Handling of negative delay values

hi sv-bc,

sv-ec is working on finalizing Mantis 890 (clocking blocks)
and amongst other things wishes to nail down exactly what
should happen when a user provides a negative value in 
a ##N procedural cycle delay.  Those who have contributed
to the discussion thus far support the idea that the 
negative value should be treated as unsigned, yielding
a large positive value, and a warning should be raised.

By analogy this raises the question of what happens when
a user supplies a negative value to a #N procedural 
delay.  Current tools disagree; we already have evidence
of two different behaviours - silent treatment of the
negative value as a large unsigned value, and silent 
clipping of the negative value to zero.

I plan to raise a Mantis item for the ## behaviour,
and I'd appreciate your input on whether it's appropriate
to extend the Mantis item to propose the same mandatory 
behaviour for #N as well.

Apologies if this has already been discussed or specified, 
but I have so far failed to find anything.

Thanks
--
Jonathan Bromley, Consultant

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