RE: FW: Question on 'above

Thank you Mr. Kamran for your reply.  Unfortunately
this answer contradicts what Ernst wrote in his reply
on the VHDL-AMS reflector (see message below).  Since
I do not have a copy of the IEEE document, I cannot
look it up, so I need to ask the question, which answer
is correct?

Thanks,

Arpad
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-----Original Message-----
From: owner-vhdl-ams@server.eda.org [mailto:owner-vhdl-ams@server.eda.org] On Behalf Of Ernst Christen
Sent: Thursday, August 24, 2006 5:35 PM
To: Muranyi, Arpad
Cc: vhdl-ams@server.vhdl.org
Subject: Re: Question on 'above

Hi Arpad,

As John Shields described, an event will happen when the expression Q - E changes sign. 
The basic question is when does the event happen. I assume you expect it to happen at the 
same time as the event on SomeRealSignal. This is not what the LRM describes. Since the 
driver of the 'ABOVE signal is owned by the analog kernel, the crossing event can only 
happen after the analog kernel has determined an ASP, because only then does it perform 
the crossing check. Now, if you study the simulation cycle, you will find that the analog 
solver determines another ASP only under two conditions: either the break flag is set, or 
Tn > Tc in step a). In the latter case the ASPs do not include Tc (the ASP at this time 
has already been determined), so you will get the crossing event at a later time than the 
event on SomeRealSignal. The only way to get what you want is to execute a break statement 
when the event occurs on SomeRealSignal. This tells the analog solver that there is a 
discontinuity on one of the waveforms it is in control of, the waveform 
SomeRealQuantity-SomeRealSignal.

Thanks.
Ernst Christen
=============================================================
-----Original Message-----
From: kamran@cad.ece.ut.ac.ir [mailto:kamran@cad.ece.ut.ac.ir] 
Sent: Saturday, August 26, 2006 1:11 AM
To: Muranyi, Arpad
Cc: zainalabedin@navabi.com
Subject: Re: FW: Question on 'above


Hello,
According to LRM, evaluation of implicit signal associated with
q'above(s)occurs in both cases,when Q is calculated,and also when S is
calculated. you can see page 174 of LRM ( IEEE Std 1076.1-1999 ). part d
of simulation cycle gurantees that  evaluation of the implicit signal
associated with q'above occurs any time S has some changes.

Regards
A. Kamran