* Fix the simple_por to (logically) isolate the 1.8V and 3.3V grounds.
This commit does the following:
(1) Corrects the xschem simple_por schematic to separate the 1.8V and 3.3V grounds.
(2) Corrects the xschem simple_por symbol to separate the 1.8V and 3.3V grounds.
(3) Corrects the xschem testbench to connect to both grounds of simple_por.
(4) Corrects the simple_por layout to remove the 1.8V logic from the
3.3V ground and connect it instead to the 1.8V ground.
(5) Extends the top-level power routing of caravel and caravan to
make a better connection to the simple_por 1.8V ground.
(6) Adds an LVS script to properly check the simple_por layout against the
xschem-generated schematic netlist.
NOTE: None of these modifications change the function of any circuit. The
1.8V and 3.3V ground nets are only logically separated in the netlists but
share the substrate. This fix cleanly defines the 1.8V and 3.3V grounds
within the simple_por, where they were previously mingled. It also ensures
that the full LVS for caravel and caravan can now include the simple_por at
the transistor level and still pass.
* Updated the GDS of simple_por (previously did not remove GDS_FILE
from the .mag file and so it just overwrote the original GDS file
with itself).
* Corrected a route to simple_por in the top level of both caravel
and caravan that was shorting to the extra metals put on top of
the substrate contact across the top (bottom, in the top level)
of the simple_por layout.
R. Timothy Edwards