RE: [sv-ac] RE: Mantis 2476 ($onehot, etc, outside assertions)

I think it is important also to be able to reference simple Boolean and
sampled value functions on the right-hand side of a continuous
assignment or a declaration assignment. They should also be allowed on
the right-hand side of a "let" declaration.

J.H.

From: owner-sv-ac@eda.org [mailto:owner-sv-ac@eda.org] On Behalf Of
Bresticker, Shalom
Sent: Tuesday, August 31, 2010 12:41 PM
To: Seligman, Erik; sv-ac@eda.org
Subject: [sv-ac] RE: Mantis 2476 ($onehot, etc, outside assertions)

$countones is a "simple boolean function", not a "sampled value
function".

At least regarding the sampled value functions, 16.9.3 says "The use of
these functions is not limited to assertion features; they may be used
as expressions in procedural code as well."

Regarding the global clocking functions, 16.9.4 says, "The global
clocking sampled value functions may be invoked only in property_expr or
in sequence_expr;

this implies that they shall not be used in assertion action blocks."

So, the only ambiguity today is about the "simple booleans".

Shalom

From: owner-sv-ac@eda.org [mailto:owner-sv-ac@eda.org] On Behalf Of
Seligman, Erik
Sent: Tuesday, August 31, 2010 6:45 PM
To: sv-ac@eda.org
Subject: [sv-ac] Mantis 2476 ($onehot, etc, outside assertions)

Hi guys-I just added this note at
http://www.verilog.org/mantis/view.php?id=2476 . Perhaps we can discuss
in today's meeting.

We need to decide not just for the functions in the original
description, but for all the assertion system functions:
$onehot $onehot0 $isunknown $sampled $rose $fell $stable $changed $past
$countones $past_gclk $rose_gclk $fell_gclk $stable_gclk $changed_gclk
$future_gclk $rising_gclk $falling_gclk $steady_gclk $changing_gclk

I think the return types are clear in the final 2009 LRM, but the
question of their usage outside assertions is left ambiguous. For each
of these categories, do we want to enable outside assertions? My
instinct is just to enable category #1.
1. Simple booleans ($onehot $onehot0 $isunknown)
2. Sampled value functions ($sampled $rose $fell $stable $changed $past
$countones)
3. Global clocking past functions ($past_gclk $rose_gclk $fell_gclk
$stable_gclk $changed_gclk)
4. Global clocking future functions ($future_gclk $rising_gclk
$falling_gclk $steady_gclk $changing_gclk)

Interestingly, 20.13 seems to have an isolated BNF production
"assert_boolean_function" that is not referenced anywhere else in the
LRM, leaving it unclear where this can be used, though the implication
is that it's restricted to assertions. Should we fix this & Annex A to
properly integrate these functions into the grammar as well?

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