From: Anders Nordstrom (andersn@nortelnetworks.com)
Date: Wed Jan 26 2000 - 14:36:19 PST
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Hi,
<p>I find that section 19.8 is not 100% clear on the time_precision aspect
<br>of the `timescale directive.
<p>As discussed at the BTF call on January 24, we should clarify the current
<br>behaviour.
<p>If a design has the same time_scale but different time_precision in
<br>different modules the behaviour is not clearly defined. If the precision
<br>1ns was used in one module and 100ps in another the simulation will
<br>run at a 100ps accuracy as stated in section 19.8 but any delays specified
<br>in the module with 1ns precision will be rounded to 1ns accuracy before
<br>being used.
<p>Draft 4 page 355 section 19.8 second paragraph under Syntax 19-8
<p>WAS:
<br>The <tt>time_precision</tt> aregument specifies how delay values are
rounded
<br>before being used in simulation. The values used are accurate to within
<br>the unit of time that is specified here. The smallest <tt>time_precision</tt>
<br>argument of all the<tt> <b>`timescale</b></tt> compiler directives
in the design determines
<br>the time unit of the simulation."
<p>PROPOSED IS:
<br>The <tt>time_precision</tt> aregument specifies how delay values are
rounded
<br>before being used in simulation. The values used are accurate to within
<br>the unit of time that is specified here <font color="#FF0000">even
if there is a smaller time_precision</font>
<br><font color="#FF0000">argument elsewhere in the design. </font>The
smallest <tt>time_precision</tt>
<br>argument of all the<tt> <b>`timescale</b></tt> compiler directives
in the design determines
<br><font color="#FF0000">the precision of</font> the time unit of the
simulation."
<br>
<p>Regards,
<p> Anders
<br>
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