From: Anders Nordstrom (andersn@nortelnetworks.com)
Date: Wed Jan 19 2000 - 13:40:13 PST
Hi,
I find that section 19.8 is not 100% clear on the time_precision aspect
of the `timescale directive.
The second paragraph under Syntax 19-8 on page 355 in Draft 4 states:
"The time_precision aregument specifies how delay values are rounded
before being used in simulation. The values used are accurate to within
the unit of time that is specified here. The smallest time_precision
argument of all the `timescale compiler directives in the design determines
the time unit of the simulation."
If a design has the same time_scale but different time_precision in
different modules the behaviour is not clearly defined. If the precision
1ns was used in one module and 100ps in another the simulation will
run at a 100ps accuracy as stated in section 19.8 but any delays specified
in the module with 1ns precision will be rounded to 1ns accuracy before
being used.
Either change the behaviour so that the smallest time_precision in the
simulation is used for all delays and parameters in the design or change
the LRM to state that delays and parameters always use the precision
of the module where they are declared regardless of the simulation
time_precision.
Regards,
Anders
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