Vacon NX User Manual

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Vacon NX User Manual Manual pdf 16 page image

16 • vacon CommissioningTel. +358 (0)201 2121 • Fax +358 (0)201 212 20545.2 MODBUS/TCP vs. MODBUS RTUCompared to the MODBUS RTU protocol, the MODBUS/TCP differs mostly in error checkingand slave addresses. As the TCP already includes an efficient error checking function, theMODBUS/TCP protocol does not include a separate CRC field. In addition to the error checkingfunctionality, the TCP is responsible for resending packets and for splitting long messages sothat they fit the TCP frames.The slave address field of the MODBUS/RTU is called unit identifier field in MODBUS/TCP.5.3 Ethernet Option Board's Modbus AddressesA Modbus/TCP class 1 functionality has been implemented in OPTCI board. The following tablelists supported MODBUS registers.Name Size Modbus address TypeInput Registers 16bit 30001-3FFFF ReadHoldingRegister16bit 40001-4FFFF Read / WriteCoils 1bit 00001-0FFFF Read / WriteInput discretes 1bit 10001-1FFFF ReadTable 3. Supported Registers5.4 Supported Modbus FunctionsFollowing table lists supporter MODBUS functions.Function Code Name AccessTypeAddress Range1 (0x01) Read Coils Discrete 00000-0FFFF2 (0x02) Read Input Discrete Discrete 10000-1FFFF3 (0x03) Read Holding Registers 16 Bit 40000-4FFFF4 (0x04) Read Input Registers 16 Bit 30000-3FFFF5 (0x05) Force Single Coil Discrete 00000-0FFFF6 (0x06) Write Single Register 16 Bit 40000-4FFFF15 (0x0F) Force Multiple Coils Discrete 00000-0FFFF16 (0x10) Write MultipleRegisters16 Bit 40000-4FFFF23 (0x17) Read/Write MultipleRegisters16 Bit 40000-4FFFFTable 4. Supported Function Codes5.5 Coil RegisterThe Coil register represents data in a binary form. Thus, each coil can only be in mode “1” ormode ”0”. Coil registers can be written using the MODBUS function 'Write coil' (5) or theMODBUS function 'Force multiple coils' (16). The following tables include examples of bothfunctions.