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Connecting a Source to a DSPF Backannotated Node
Post-Layout Simulation
DSPF Backannotation Examples
It is possible to connect a source to a node that is backannotated with DSPF. This might be
useful to insert a voltage or current source to a specific node to check a critical path. However,
after DSPF extension, the original node might be expanded in several nodes, and there might be
no path remaining between the extra source and the network, that is, the extra source no longer
has a connection to the network. This is because the extra source was not in the design when
DSPF information was created. The solution is that nodes connected to that extra source are not
expanded by DSPF. Eldo can detect such situations when the extra source is instantiated from
the top of the design and connected to a node at a lower level of hierarchy, using the full node
pathname. For example:
.SUBCKT INV in out
*...
R1 in internal 1k
*...
.ends
X1 in out INV
v1 X1.internal 0 5
!full pathname usage
Eldo will detect this configuration, and DSPF instructions will be ignored on node X1.internal.
This is similar to the command: .IGNORE_DSPF_ON_NODE X1.internal.
However if the extra source is added at the same level as the nodes (for example all at the top),
Eldo will only be able to issue a message that the node is connected to a single device only, and
will indicate that there is a possible DSPF connection problem. You must then manually add the
command .IGNORE_DSPF_ON_NODE on that node to deal with that specific situation.
Related Topics
SPEF Backannotation
DSPF File Structure
Eldo Post-Layout Commands
Eldo Post-Layout Options
Example 21—Post-Layout Simulation using DSPF
Eldo® User's Manual, 15.3 397