Yes. This feature was added in 2013. Ensure that both the datalogger operating system and the SDM-SIO1 firmware are up to date. Using an SDM-SIO1, the datalogger can be a Modbus client (master) or host (slave), although the intended and most common use is for client (master) operation. In CRBasic, use the SerialOpen() instruction to configure the SDM-SIO1 interface and the ModBusMaster() instruction to issue Modbus commands.