The script flow.txt is the command sequence for synthesis, simulation,
P&R, DRC, LVS and GDS and CIF file creation.

The script syn_loop is the synthesis part which loops vasy, boom, boog
and loon to find the quickest netlist. The scripts vasy_loop etc do
each synthesis part separately. There are some timeouts to stop an
excessive run time which can be changed for a more exhaustive loop.

The loon loop alternates between the 0fF and 6fF wireload libraries
to find the netlist with the shortest critical path with the 6fF
wireload.

A script find_crit_path writes out the critical path for the 0fF and
6fF wireload libraries.

The placement from ocp is modified to insert a two track wide feedthru
cell at the left and right to ensure each cell row is properly
terminated with well and substrate tie downs. A script also merges
adjacent feedthru cells that are wider than 2 tracks.

Routing is done twice, once with metal-2 horizontally and once with
metal-2 vertically.

After routing the netlist, a script adds pieces of metal around the
vias to give a 2 lambda end overlap of metal. This can give DRC errors
to adjacent metal, so a loop runs DRC; adds layout blockages at the
DRC co-ordinates; and reruns the router with these blockages. The loop
continues until there are no more DRC errors.

This means that the layout can be DRC checked with vsc013.rds, which
checks for a 2 lambda via end overlap. The vsc013x.rds file which
checks for a 1 lambda via overlap has to be used on layout directly
written by NERO.

Critical path delay is 399 ps
Area is                552 um^2
Gate count              80
Occupancy               84%



NOTE THE NETLIST MANIPULATION AT THE END OF THE syn_loop SCRIPT. THERE
IS A 1-BIT VECTOR IN THE NETLIST WHICH CAUSES THE LATER LVS TO FAIL.
USING X2Y REPLACES THIS.
