Well, there are demo versions of Schneider Automation softwares, not exaclty freeware softwares.
You can find demo softwares for PL7, Concept and Proworx at "www.modicon.com":http://www.modicon.com .
Each one has its specifics restrictions.
First, which TSX PLC are you referring to. Almost every Modicon PLC has TSX in front of it's name.
Second, the only thing you're going to get for free are limited demo versions of the software. If you're talking about the TSX Quantum, Momentum, or Compact, you can use Concept. If you're talking about Quantum, Momentum, Compact, Modicon Micro, 984, you can use Proworx NXT or Proworx 32. If you're talking about the TSX Micro and TSX Premium (TSX37 and TSX57) you can use PL7 Pro. All others are legacy and you're not going to find a trial version of the legacy packages.