---
name: "loon"
section: "1"
platform: "linux"
package: "alliance"
version: "5.1.1-3"
release: "Debian 10 (Buster)"
platforms: ["linux"]
url: "https://new.carta.tech/loon"
---

# loon(1)

## NAME

- LooN - Local optimizations of Nets.

  ## SYNOPSIS

- ***loon*** \[-hmxlo\] *input\_file* *output\_file* \[*lax\_file*\]

  ## DESCRIPTION

***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)](/lax/5.md) 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\

## OPTION

- ***-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.\

## 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.

## EXAMPLE

You can call ***loon*** as follows :\
\
\
 	loon alu alu\_loon

## SEE ALSO

[loon(1)](/loon/1.md), [boog(1)](/boog/1.md), [boom(1)](/boom/1.md), [lax(5)](/lax/5.md), [vbe(5)](/vbe/5.md), [proof(1)](/proof/1.md), [asimut(1)](/asimut/1.md), [vhdl(5)](/vhdl/5.md), [ocp(1)](/ocp/1.md), [nero(1)](/nero/1.md), [sxlib(5)](/sxlib/5.md).\