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loon.1alc - Man Page

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 information 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.

-o input_file

Overwrites the source file if no output_file is given. This can be useful 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 explicitly the LAX parameter file name.

Environment Variables

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

See Also

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

Referenced By

boog.1alc(1), lax.5alc(5), sxlib.5alc(5), syf.1alc(1), vasy.5alc(5), vbe.5alc(5), vhdl.5alc(5).

Sept 01 2000 ASIM/LIP6 CAO-VLSI Reference Manual