Core layout generation
----------------------

Incremental design relies on hierarchy. Before you design the
core to pads netlist, the circuit core must be successfully built.
In the ALLIANCE design metholdology, layout generation relies on:
1) standard-cells placement (automatic or manual).
2) automatic routing of standard-cells.

The ALLIANCE CAD system can actually perform these two steps
simultaneously. The scr tool is a placement/router tool that can
produce automatically the layout view from a netlist description.

As stated in the previous section, before you run scr, you
must specify environment variables. No need to say that these
variables will deal with physical aspects of the circuit.

First, you must specify the input layout format you use for
the standard-cells. The ALLIANCE distribution tape only
contains ap symbolic layout files so you must issue the following
command:

> setenv MBK_IN_PH ap

This command instructs scr to use ap representations of cells as an
input. Remember that MBK_CATA_LIB is still set, so ALLIANCE knows
where to find cells.

Second, you must accordingly specify the output layout format.
Again, the format is ap, so

> setenv MBK_OUT_PH ap

This command instructs scr to use ap representation of cells as an
output.

Everything is now ready for the placement/routing phase.
The command is:

> scr -p -r addaccu addaccu 

The first addaccu stands for structural netlist addaccu.vst.

The second addaccu is the resulting layout, addaccu.ap.
Option -p signifies automatic placement
Option -r signifies automatic routing

Once scr has been executed, the core layout is completed.

Press <return> to continue.
