Specparam vs. parameter

[Evan Lavelle]

The LRM seems unclear on where specparams must be used, and where
parameters may be used instead. p222 says that path delay values must
be "constant expressions containing literals or specparams", and p240
says

Like expressions for module path delays, timing check limit values are constant expressions that can include
specparams.

The BNF shows path delay values as constant_mintypmax_expressions, and
timing check limits as expressions, but both of these are presumably
errors.

A straw poll of 3 sims shows that one will only accept literals and
specparams in a $setuphold, and the other two will accept literals,
specparams, and parameters (which is obviously a lot more useful).

Any clarifications, or thoughts on what the intention is/was?

Thanks -

Evan

 

[Jonathan Bromley]

On Thu, 11 Oct 2007 09:56:53 +0100, Evan Lavelle <nospam@nospam.com>
wrote:

The LRM seems unclear on where specparams must be used
[...]
Any clarifications, or thoughts on what the intention is/was?

see my other post... I thought that specparams were intended to
be overrideable using SDF backannotation, whereas parameters
are overridden in the hierarchy? And I *thought* that you are
supposed only to use specparams for delays in specify blocks -
I didn't think that parameters worked there. Could be wrong
about that though; I'm not heavily into all that gate-level
and library-hacking stuff.
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[Evan Lavelle]

On Thu, 11 Oct 2007 16:04:46 +0100, Jonathan Bromley
<jonathan.bromley@MYCOMPANY.com> wrote:

On Thu, 11 Oct 2007 09:56:53 +0100, Evan Lavelle <nospam@nospam.com
wrote:

The LRM seems unclear on where specparams must be used
[...]
Any clarifications, or thoughts on what the intention is/was?

see my other post... I thought that specparams were intended to
be overrideable using SDF backannotation, whereas parameters
are overridden in the hierarchy? And I *thought* that you are
supposed only to use specparams for delays in specify blocks -
I didn't think that parameters worked there. Could be wrong
about that though; I'm not heavily into all that gate-level
and library-hacking stuff.

That's my understanding as well, but I've got a big-$ sim and a
medium-$ sim which disagree. It does seem to be an entirely artificial
and unhelpful restriction, so perhaps they just ignored it...

Evan