Maximim number of devices on Win-Tech ModSim

I was trying to simulate with Win-Tech ModSim32 a modnet communication with 152 devices on the same port, every devices with Holding register and Input register connected. But when I connect all the devices at the same time, I cannot read every devices: all the times, I cannot read about 26-27 devices, wich ones depends on the order I open the devices files in ModSim. I tried to read with CitectSCADA and with ModScan, having the same result. ModSim seems to be busy with all the devices connected and if I put devices on two port, it works fine.

Anyone have had the same problem?