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LooN - Local optimizations of Nets.


loon [-hmxlo] input_file output_file [lax_file]


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


-h Help mode. Displays possible uses of loon.

-o input_file
Overwrites the source file if no output_file is given. This can be usefull if
you don't want several netlist files.

-m optim_mode
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.

-x xsch_mode
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.

-l lax_file
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

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

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

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