Chapter 9: Tools
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9-7-2: NCC Commands |
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To compare two cells, use these commands (in menu Tool / NCC):
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Schematic and Layout Views of Cell in Current Window
Use a heuristic to figure out what to compare against the cell in
the current window. If the current cell is a schematic then
compare it against some layout cell in the same cell group. If the
current cell is a layout then compare it against some schematic
cell in the same cell group. Since most cell groups have one
layout cell and one schematic cell, this form of the NCC command is
usually the most convenient.
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Cells from Two Windows
Compare the two cells that are displayed in the two opened windows
(there must be exactly two windows). This is useful when the
schematic and layout are not in the same cell group. The command
can also be used to compare schematics with schematics or layout
with layout. However, the command refuses to compare icon cells
since icons cells don't have defined connectivity.
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Copy Schematic User Names to Layout
and Copy All Schematic Names to Layout
For each pair of matching schematic and layout cells, rename networks
and nodes
in the layout cell to have the same name as the equivalent networks
in the schematic cell. The first command copies only user-assigned names
from the schematic to the layout; the second command copies all names.
Furthermore, it only changes the names
of layout
networks and nodes
that have no user-assigned names. If a layout network
or node has
a user-assigned name that does not match the schematic then this
command prints a warning. This command also warns when non-equivalent
networks or nodes have the same user-assigned name.
Notes:
-
These commands use the result
generated
by the most recent run of NCC. That NCC run should be hierarchical
without
size checking.
-
These commands clear the saved result from the last run of NCC.
If you need to run a command that needs the last result, for example
"Highlight Equivalent", then you must rerun NCC.
-
Highlight Equivalent
Highlight the network or node that is equivalent to the currently
selected
network or node, using the result of the most recent NCC run.
The user should be aware of a number of limitations:
-
This command works best for networks in the top
level cells compared by the most recent NCC run.
-
This command also works for nodes in the top
level cells compared by the most recent NCC run as long
as those nodes are primitive transistors or were treated as
primitives because NCC compared them hierarchically.
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Because NCC combines MOS transistors that are in series
into a single NMOS_*STACK,
NCC
can't find equivalents for certain networks and nodes.
For example,
when NCC merges two series MOS transistors into a single
NMOS_2STACK it removes the network between them from NCC's
database. Therefore if you click on that network and ask
to highlight the equivalent, NCC won't be able to find
an equivalent.
-
Because NCC combines MOS
transistors that are in parallel, it can't find equivalents
for certain networks and nodes. For example when NCC
detects two parallel MOS
transistors, it removes one from NCC's database but adds
it's width to the other. Therefore if you click
on the transistor that was discarded and ask to highlight the equivalent, NCC
won't be able to find an equivalent.
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Run NCC for Schematic Cross-Probing
This command runs NCC and saves the net associations between schematic and layout.
The user can generate a Spice netlist (for example) from an Electric layout cell.
Simulating this netlist will result in a waveform file that uses layout hierarchy and net names.
If this waveform file is loaded into Electric, it cannot be cross-probed from the schematic.
It can be cross-probed from the layout, but that is often difficult to do.
In this case, the user can run this NCC command,
which will save net associations between schematic and layout.
Then, the user can cross-probe from the schematic,
and Electric will automatically translate the schematic net to the appropriate layout net contained in the waveform file.
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Add NCC Annotation to Cell
This is a submenu that allows user to select which NCC annotation
to add to a cell. Note that the designer should replace text surrounded
by angle brackets: "< >". See Section 9-7-4
on "NCC Annotations" for a description of each NCC annotation.
