errata/74: : 4.1.14: unclear examples of illegal concatenations

From: Shalom Bresticker (Shalom.Bresticker@motorola.com)
Date: Wed Jul 17 2002 - 05:34:21 PDT

Precedence: bulk

>Number: 74
>Category: errata
>Originator: Shalom Bresticker <Shalom.Bresticker@motorola.com>
>Description:

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Section 4.1.14 contains the following:

Another form of concatenation is the replication operation. The first
expression shall be a non-zero, non-X and non-Z constant expression, the
second expression follows the rules for concatenations. This example
replicates "w" 4 times.

{4{w}} // This is equivalent to {w, w, w, w}
a[31:0] = {1`b1, {0{1`b0}} }; //illegal. RHS becomes {1`b1,;
a[31:0] = {1`b1, {1`bz{1`b0}} }; //illegal. RHS becomes {1`b1,;
a[31:0] = {1`b1, {1`bx{1`b0}} }; //illegal. RHS becomes {1`b1,;

The comments on the three examples of illegal concatenations look
strange.
"RHS becomes {1 b1,;" looks cut off.

I propose to just leave them as "illegal". Anyone who reads the
preceding paragraph will immediately understand the reason. The existing
comments is just confusing. 

--
Shalom Bresticker                           Shalom.Bresticker@motorola.com
Design & Reuse Methodology                             Tel: +972 9 9522268
Motorola Semiconductor Israel, Ltd.                    Fax: +972 9 9522890
POB 2208, Herzlia 46120, ISRAEL                       Cell: +972 50 441478

"The devil is in the details."

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Section 4.1.14 contains the following:
<p>Another form of concatenation is the replication operation. The first
expression shall be a non-zero, non-X and non-Z constant expression, the
second expression follows the rules for concatenations. This example replicates
"w" 4 times.<tt></tt>
<p><tt>{4{w}} // This is equivalent to {w, w, w, w}</tt>
<br><tt>a[31:0] = {1`b1, {0{1`b0}} };&nbsp;&nbsp;&nbsp; //illegal. RHS
becomes {1`b1,;</tt>
<br><tt>a[31:0] = {1`b1, {1`bz{1`b0}} }; //illegal. RHS becomes {1`b1,;</tt>
<br><tt>a[31:0] = {1`b1, {1`bx{1`b0}} }; //illegal. RHS becomes {1`b1,;</tt>
<p>The comments on the three examples of illegal concatenations look strange.
<br>"<tt>RHS becomes {1 b1,;" </tt>looks cut off.
<p>I&nbsp;propose to just leave them as "illegal". Anyone who reads the
preceding paragraph will immediately understand the reason. The existing
comments is just confusing.
<pre>--&nbsp;
Shalom Bresticker&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Shalom.Bresticker@motorola.com
Design &amp; Reuse Methodology&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Tel: +972 9 9522268
Motorola Semiconductor Israel, Ltd.&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Fax: +972 9 9522890
POB 2208, Herzlia 46120, ISRAEL&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Cell: +972 50 441478

"The devil is in the details."</pre>
&nbsp;</html>

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