Re: [sv-ec] Synchronous drives. - obsolete description in LRM

From: <jonathan.bromley_at_.....>
Date: Fri Mar 13 2009 - 07:07:20 PDT
Daniel

> 14.16 Synchronous drives. 
> There is:
> "The second form of the synchronous drive uses the intra-assignment 
> syntax. An intra-assignment event_count specification also delays 
> execution of the assignment. In this case, the process does not 
> block, and the right-hand expression is evaluated when the 
statementexecutes."
> 
> There is no 2nd form as in 1800-2009 it was removed. This paragraph 
> need to be rewriten.

Oh dear, this is definitely a problem.  I can't believe this slipped
through all the 890 discussions, but obviously it did.  I suspect 
it is caused by BNF and text getting out-of-sync.

The following examples clearly and correctly capture the result
of the Mantis 890 discussions: ##N in any procedural context, even 
if used to delay a synchronous (clocking) drive, means delay by
N cycles of the DEFAULT clocking.  But ##N as an intra-assignment
delay, which is legal only on the RHS of a synchronous drive,
means postpone the drive by N cycles of the TARGET CLOCKVAR's
clocking.

Not only the paragraph you mention, but also the immediately
previous paragraph, is misleading.  The italicised "event_count"
does not appear anywhere else in the LRM.

I've raised Mantis 2596 to address this, and will post a proposed 
text change shortly.


> There is also lack of illegal drive example given : data[3:0] <= 4?h5;

Sorry, I don't really understand what you're asking here;
I agree that there are no illegal examples, but I'm not sure what
value they would bring.
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Received on Fri Mar 13 07:08:17 2009

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