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LOON(1) CAO-VLSI Reference Manual LOON(1)



This software belongs to the ALLIANCE CAD SYSTEM developed by the ASIM team at LIP6 laboratory of Université Pierre et Marie CURIE, in Paris, France.

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loon is a CAD tool that allows to remove fanout problems within a gate netlist and also to optimize the delay. The netlist can be hierarchical and is flattened if necessary. loon runs in batch mode and a parameter file can be used (see man lax) to parametrize optimization by adding informations on outputs (fanin), inputs (fanout, delay) and by setting general parameters such as optimization level. loon permits to compute delays of gates in the netlist and gives the critical path in the netlist. The global optimization of loon performs gate repowering to decrease the critical path delay and global capacitance. Buffers are only inserted in critical path.

lax Parameter file description
The lax file is common with other logic synthesis tools and is used for driving the synthesis process. See lax(5) manual for more detail.

lax uses a lot of parameters to guide every step of the synthesis process. Some parameters are globally used (for example, optimization level whereas others are specifically used (load capacitance for the netlist optimization only). Here is the default lax file (see the user's manual for further information about the syntax of the '.lax' file):

Optimization mode = 2 (50% area - 50% delay)
Input impedance = 0
Output capacitance = 0
Delayed input = none
Auxiliary signal saved = none


Help mode. Displays possible uses of loon.
Overwrites the source file if no output_file is given. This can be usefull if you don't want several netlist files.
Optimization mode. Can be defined in lax file, it's only a shortcut to define it on command line. This mode number has an array defined between 0 and 4. It indicates the way of optimization the user wants. If 0 is chosen, the circuit area will be improved. On the other hand, 4 will improve circuit delays. 2 is a medium value for optimization.
Generate a '.xsc' file. It is a color map for each signals contained in output_file network. This file is used by xsch to view the netlist. By choosing level 0 or 1 for xsch_mode, you can color respectively the critical path or all signals with delay graduation.
Just another way to show explicitely the LAX parameter file name.


The following environment variables have to be set before using loon :

MBK_CATA_LIB gives the auxiliary paths of the directories of input files (behavioural description).

MBK_TARGET_LIB gives the path (single) of the directory of the selected standard cell library.

MBK_IN_LO gives the input format of the structural description.

MBK_OUT_LO gives the output format of the structural description.


You can call loon as follows :
loon alu alu_loon


loon(1), boog(1), boom(1), lax(5), vbe(5), proof(1), asimut(1), vhdl(5), ocp(1), nero(1), sxlib(5).


This tool is under development at the ASIM department of the LIP6 laboratory.
We need your feedback to improve documentation and tools.

Sept 01 2000 ASIM/LIP6