138 • vacon parameter descriptions99.17 Modbus RTUVacon 20 has a built-in Modbus RTU bus interface. The signal level of the interfaceis in accordance with the RS-485 standard.The built-in Modbus connection of Vacon 20 supports the following function codes:9.17.1 Termination resistorThe RS-485 bus is terminated with termination resistors of 120 ohms in both ends.Vacon 20 has a built-in termination resistor which is switched off as a default (pre-sented below). The termination resistor can be switched on and off with the righthand dip switch located above IO-terminals in the front of the drive (see below).Figure 9.27: Vacon 20 I/O9.17.2 Modbus address areaThe Modbus interface of Vacon 20 uses the ID numbers of the application parametersas addresses. The ID numbers can be found in the parameter tables in chapter 8.When several parameters / monitoring values are read at a time, they must be con-secutive. 11 addresses can be read and the addresses can be parameters or moni-toring values.Note: With some PLC manufacturers, the interface driver for Modbus RTU commu-nication may contain an offset of 1 (the ID number to be used would then subtract 1).Functioncode Function name Address Broadcastmessages03 Read Holding Registers All ID numbers No04 Read Input Registers All ID numbers No06 Write Single Registers All ID numbers Yes16 Write multiple registers All ID numbers YesTable 9.3: Modbus RTU4 5 13 14 15 16 20181 2 3 6 7 8 9 1022 23 262425AI2 GND DO- DI4 DI5 DI6 AO DO+ R13 R14 * R24+10VAI1 GND 24V DI-C DI1 DI2 DI3 A B R21 R22DIEnco NorAOV mAAI2V mARS485- termONOFFJ500Phone: 800.894.0412 - Fax: 888.723.4773 - Web: www.clrwtr.com - Email: info@clrwtr.com
