You can use either Lookout or Labview to do so. NI OPC server supports the Mitsubishi FX-series driver. Lookout has it. It is said to support all FX-series models through March, 1997.
But, the only PLC model can be selected for this series when programming is 24MR. So we need to make sure the difference between 24MR and 20MR. The communication protocol may be the same, but the registers are not sure.
Ryan Shi
National Instruments