[Fwd: Re: LRM 5.x: Unclear about when block refires on same event that changed]

From: Shalom Bresticker (Shalom.Bresticker@motorola.com)
Date: Wed Feb 14 2001 - 01:30:35 PST

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<th ALIGN=RIGHT VALIGN=BASELINE NOWRAP>Subject: </th>

<td>Re: LRM 5.x: Unclear about when block refires on same event that changed</td>
</tr>

<td>"M Ciletti" <eagle64@email.msn.com></td>
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<th ALIGN=RIGHT VALIGN=BASELINE NOWRAP>References: </th>

<div
style="BACKGROUND: #e4e4e4; FONT: 10pt arial; font-color: black">From:
<a href="mailto:VhdlCohen@aol.com" title="VhdlCohen@aol.com">VhdlCohen@aol.com</a></div>

<div style="FONT: 10pt arial">To: <a href="mailto:vlog-synth@eda.org" title="vlog-synth@eda.org">vlog-synth@eda.org</a></div>

<div style="FONT: 10pt arial">Sent: Tuesday, February 13, 2001 1:41
PM</div>

<div style="FONT: 10pt arial">Subject: Re: LRM 5.x: Unclear about
when block refires on same event that changed</div>
In a message dated 2/13/01
11:51:19 AM Pacific Standard Time,
 <a href="mailto:eagle64@email.msn.com">eagle64@email.msn.com</a>
writes:
 <<
<blockquote
style="PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: #0000ff 2px solid; MARGIN-RIGHT: 0px"
TYPE="CITE">The
"always" behavior in your example parks for 10 time steps, then
 complements a, but notice
that the event control expression cannot see this
 because the activity is
located at the statement where the complement is
 taking place. Control
does not return to the event control expression
 until all of the sequential
statements in the behaviror have completed
 execution. When the
event control expression is finally awake, it does not
 see what happened in the
past.>></blockquote>

OK, so WHERE
in the LRM does it say that "Control does not return
to the
 event control
expression until all of the sequential statements in the
 behaviror have
completed execution"?
Section 5.4 shows
the Verilog simulation reference model
 It states:
 while (there
are events) {
 if (no active
events) {
 ...
 
}
 }
 E = any active
event;
 if (E is an
update event) {
 
update the modified object;
 
add evaluation events for sensitive processes to event queue;
 } else
{ /* shall be an evaluation event */
 evaluate
the process;
 add update
events to the event queue;
 }
 }
Also, in 5.6.3
Blocking assignment states "When the process is returned (or
 if it returns
immediately if no delay is specified), the process performs the
 assign-ment
to the left-hand side and enables any events based upon the
 update of the
left-hand side.
From the above
two statements, it would seem that at time 10, "a" becomes an
 updated event.
 Where am I wrong?
 
always(@ a or
@ b) // P1 block
 
begin
 
#10 a =~ a;
 
c = b;
 
end
 
 
 
 
 
 
------------------------------------------------------------------------------
--------------------------------------
 Ben Cohen
Publisher, Trainer, Consultant (310) 721-4830
 http://www.vhdlcohen.com/>
vhdlcohen@aol.com
 Author of following
textbooks:
 * Component
Design by Example ... a Step-by-Step Process Using
 VHDL
with UART as Vehicle", 2001 isbn 0-9705394-0-1
 * VHDL Coding
Styles and Methodologies, 2nd Edition, 1999 isbn 0-7923-8474-1
 * VHDL Answers
to Frequently Asked Questions, 2nd Edition, isbn 0-7923-8115
 ------------------------------------------------------------------------------
--------------------------------------</blockquote>

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