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Document time scale in netlists.

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steve 2000-07-23 18:06:15 +00:00
parent 81dab9c572
commit 4f75d04a42
1 changed files with 27 additions and 1 deletions
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netlist.txt
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@ -16,7 +16,7 @@
* along with this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
*/
#ident "$Id: netlist.txt,v 1.9 2000/07/14 06:12:57 steve Exp $"
#ident "$Id: netlist.txt,v 1.10 2000/07/23 18:06:15 steve Exp $"
Note that the netlist.h header contains detailed descriptions of how
@ -269,7 +269,33 @@ recurse. (The elaboration process does reserve the right to flatten
some task calls. C++ programmers recognize this as inlining a task.)
TIME SCALE IN NETLISTS
The Design class and the NetScope classes carry time scale and
resolution information of the elaborated design. There is a global
resolution, and there are scope specific units and resolutions. Units
and resolutions are specified as signed integers, and interpreted as
the power of 10 of the value. For example, a resolution "-9" means
that "1" is 1ns (1e-9). The notation supports units from -128 to +127.
It is up to the back-ends to interpret "-4" as "100us".
Delays are expressed in the netlist by integers. The units of these
delays are always given in the units of the design precision. This
allows everything to work with integers, and generally places the
burden of scaling delays into elaboration. This is, after all, a
common task. The Design::get_precision() method gets the global design
precision.
Each NetScope also carries its local time_units and time_precision
values. These are filled in during scope elaboration and are used in
subsequent elaboration phases to arrange for scaling of delays. This
information can also be used by the code generator to scale times back
to the units of the scope, if that is desired.
$Log: netlist.txt,v $
Revision 1.10 2000/07/23 18:06:15 steve
Document time scale in netlists.
Revision 1.9 2000/07/14 06:12:57 steve
Move inital value handling from NetNet to Nexus
objects. This allows better propogation of inital