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The Net Selections button in the Extract Menu brings up
the Path Selection Control panel. This panel enables
extraction-specific selection modes for groups, nodes, and connected
conductor paths (wire nets). It is separate and distinct from the
normal object and subcell selection. Command buttons in the panel
replace menu buttons and modes found in other commands in earlier
releases of Xic, in particular the group/node selection found in
the View Extraction mode, and the Show Paths and Quick Paths commands found in the Extract Menu of Xic
releases 3.1.4 and earlier are now available from this panel.
The Net Selections Button: Path Selection Control Panel
There are three basic selection modes available, which are set from
the top row of buttons in the panel. Similar to normal selections,
one clicks on an object in a drawing window. The object must be on a
visible and selectable layer. Other selection specifications as found
in the Selection Control Panel apply as well. In particular,
one can choose the types of objects that are selectable, and the
search-up mode. In search-up mode, layers are searched from bottom to
top, rather than the default top to bottom, in physical mode. This
affects the conductor chosen if the user clicks over more than one
- Select Group/Node
When active, clicking on a conducting object in the current cell in a
physical window will highlight all objects of the current cell in that
conductor group. In electrical windows displaying the same cell, the
corresponding node connections and wires will be highlighted.
Clicking on a connection point or wire in an electrical window will
highlight that node, and also highlight the corresponding group in
Physical objects are ``conducting'' if the Conductor keyword was
applied (directly or by inference) to the layer of the object.
If the Select Path button is also pressed while in this mode,
the conducting path, as it recurses into subcells, will also be shown
in physical windows.
Pressing the p key will toggle the state of the Select
Path button and the display of recursive conductor paths.
With the mouse pointer in a physical window, typing a group number
followed by Enter will switch to the display of that group and
corresponding node. Similarly, in an electrical window, entering a
node name or number followed by Enter will switch the display to
the entered node and corresponding group. However, entering a name
will probably trigger all kinds of accelerators, including those for
this command, so there is a trick. Type a single or double quote
character, followed by the node name. The quote character will
inhibit recognition of accelerators. Since the keypress buffer length
is only 16 characters, long node names can't be entered in this
manner, the equivalent node number can be entered or some other method
used to select the node.
In electrical mode, the command works with the Node Mapping
Editor when visible. The currently selected node will always be
highlighted in the node list panel of the editor. Selecting a node in
the editor will highlight that node/group in the display windows.
- Select Path
When the Select Group/Node button is also pressed, physical
windows will display the conducting path of the currently selected
group descending into subcells. Otherwise, this button initiates a
different command for displaying conductor paths recursively. This
mode is available in physical mode only. Clicking on a conducting
object will highlight the conductor path containing that object.
There is no selection or indication of the corresponding electrical
node, nor will clicking in an electrical window have any effect in
this mode. The clicked-on object need not be in the current cell (as
is required for group/node selection), but must be within the search
depth. The path generation algorithm makes use of the extraction
system, and observes extracted devices and exclude directives as
provided to the extraction system.
Only one path can be shown at a time. Clicking on another object will
rebuild a path from the second object, erasing the original path, or
it is possible to select a sub-path, it that feature is enabled.
If a dark-field ground plane is used, clicking on the painted areas
(holes in the ground plane) will select the ground group, as will
clicking on any other object which is connected to ground (group 0).
- "Quick" Path
This command is similar to the Select Path command, but does not
use the extraction system, except for establishing conducting layers
and connections through vias. In particular, there is no information
about devices and other extraction constraints established at higher
levels. It may be useful for tracing wire nets, while skipping the
sometimes lengthly extraction operation.
The "Quick" Path algorithm, unlike Show Paths, will ignore
layers that are set invisible.
Since extraction is not used, there is no concept of devices, so that
results may not be as expected, and not be as seen with the Show
Paths mode. For example, consider MOS devices. Since, the source
and drain are connected to a common area of the ``active'' layer,
which is (usually) a Conductor, the simple algorithm used in
this mode will interpret the source and drain as being connected
together, since it does not recognize the MOS device. As a
consequence, all wire nets are likely shorted together in this mode!
In order to get meaningful results, it may be necessary in this case
to temporarily remove the Conductor keyword from the active
layer. This can be accomplished with the Tech Parameter Editor
in the Attributes Menu.
The remaining buttons and controls in the panel provide options or
modes while the selections are active.
- "Quick" Path ground plane handling
This menu applies only to the "Quick" Path selection mode, and
sets the ground plane handling method. This tracks the setting of the
QpathGroundPlane variable. If a dark-field ground plane (GroundPlaneClear keyword) has been specified in the technology file,
the implied connectivity to ground is similar to that in force for the
extraction system. There are three choices for handling the ground
- Use ground plane if available
This is the default. If an inverted ground plane has already been
created and is current, it will be used when determining paths. If
the ground plane does not have a current inversion, the absence of the
layer will imply a ground contact, as in extraction without the MultiNet keyword. This choice avoids the sometimes lengthly
inversion computation, but makes use of the inversion if it has
already been done. The inversion is performed during extraction.
- Create and use ground plane
If the extraction system would use an inverted ground plane, it will
be created if not already present and current. The path selection
will include the inverted layer.
- Never use ground plane
The "Quick" Path mode will never use the inverted ground plane.
- Search path depth
This control and associated buttons apply when the Select Path
or "Quick" Path modes are in effect. It determines the depth to
recurse to when the conductor path is being constructed. If 0, only
objects in the current (top-level) cell will be considered. The depth
can be entered directly, or by clicking the up/down buttons, or by
pressing the 0 or All buttons.
While the command is active, the expansion depth can also be changed
with the -, +, n, and a keys. These
decrement, increment, set to 0, and set to maximum, the depth,
When the depth changes, the path, if one is being shown, will be
redrawn, if possible (the original object must be above the new
- "Quick" Path use Conductor
If this check box is not checked, only objects on layers with the Routing attribute applied will be considered for inclusion in the
extracted path. If checked, objects on layers with the Conductor attribute will be allowed. The Routing attribute
implies Conductor, but may be more restrictive.
The QpathUseConductor variable tracks the state of this check
- Blink highlighting
When this box is checked, the highlighting in physical windows will
blink. When unset, the highlighting will use the static highlighting
color. Associated highlighting in electrical windows will always
With a path being displayed, pressing the h key will toggle the
- Enable sub-path selection
This check box enables sub-path selection while in the Select
Path or "Quick" Path modes.
When a path is displayed, the user can click on two objects in the
path, and only the ``sub-path'' connecting the two objects will be
highlighted. If the two objects are connected in multiple ways, the
algorithm will select one (which may not be the most direct). If Shift is held while clicking on an object in the path, the object
will be deselected and not considered as part of the path. This can
be used to coerce a desired sub-path. When a sub-path is displayed,
clicking on any non-selected object will display the full path
containing that object.
- Load Antenna file
This button applies to the Select Path mode only. Pressing this
button will load a previously-generated antenna report file (from the
!antenna command) for the current cell, and ask the user for a
net number found in the file. The conductor path corresponding that
that net number will be highlighted.
Pressing the f key while in Select Paths mode will also
query an antenna report file in a similar manner.
- To trapezoids
Pressing this button will decompose the geometric objects which
comprise the currently shown physical conductor path into trapezoids.
This has no effect on ``real'' objects in the database or in the
extraction system, only the temporary objects used to display the
This can be useful in conjunction with the sub-path selection
capability, to enable breaking a path by deselecting parts of an
object that are separate as trapezoids. It may also be useful as a
prelude to the Save operations in some cases.
Pressing the t key with a path displayed will also convert the
path to trapezoid representation.
- Save path to file
If a physical conductor path is being displayed, this button enables
saving the objects that comprise the path to a native cell file. Only
the selected objects will be exported. If the path has been converted
to trapezoids, the trapezoid representation will be exported.
Pressing the button brings up a small pop-up where the user can give a
cell/file name. The resulting file can be read into Xic at a later
time for further processing, or for conversion to another file format.
By default, the via layers are not included in the file, only the
conductors. The two check boxes below the button allow saving the
vias and other associated layers as well.
Pressing the s key with a path displayed will also save the path
to a file in a similar manner.
- Path file contains vias
This check box applies when the Save path to file button is
used. When checked, the via objects that connect layers will be
included in the generated path. If not checked, only the metal layers
that constitute the path will be included in the file. The via layers
are those that have the Via keyword defined in the technology
file. The file will included the objects on the via layers, clipped
to the intersection area of the two associated conductors.
- Path file contains via check layers
This check box applies when Save path to file is used, and
the Path file contains vias check box is checked.
The Via keyword line in the technology file contains an optional
layer expression, which must be ``true'' for an actual connection to
be indicated. For example
Via SBST MET1 DIFF&PPLS
This line would indicate that the layer containing this line forms a
via between conductors SBST and MET1 only in the presence of layers
DIFF and PPLS.
When this check box is checked, the file will contain the layers
needed for the checking expression (DIFF and PPLS), clipped to the via
layer objects. If not checked, the file will contain only the vias
that meet the check criteria, but the layers needed for checking (DIFF
and PPLS) will not appear.
With this box checked, the file can be loaded into Xic and
extraction run, and the (single) net will be completely identified.
This may not be the case if check layers are missing, and certainly
won't be the case if via layers are omitted.
The two via inclusion check boxes track the state of the PathFileVias variable. If this variable is set as a boolean (i.e.,
to no value), then vias will be included, and check layers will not be
included. If the variable is set to any text, the check layers will
also be included.
Next: Resistance Measurement
Up: The Extract Menu: Extraction
Previous: The Misc Config Page
Stephen R. Whiteley