Modbus Slave Modbus Slave is for simulating up to 32 slave devices in 32 windows!. Speed up your PLC programming with this simulating tools. Start programming and test before you receive your slave device from supplier. Data contained with any open document is accessible to the master application. Same user interface as Modbus Poll. Support function 01, 02, 03, 04, 05, 06, 15, 16, 22 and 23.