Chapter 8. Modbus/TCP ServerGFK-2224Q January 2017 137Modbus Holding Register TableThe Modbus Holding Register table is mapped exclusively to the CPU Register (%R) table.Applicable Functions▪ Read Multiple Registers▪ Write Multiple Registers▪ Write Single Register▪ Mask Write Register▪ Read/Write Multiple RegistersModbus Input Register TableThe Modbus Input Register table is mapped exclusively to the CPU Analog Input (%AI) table.Applicable Functions▪ Read Input RegistersModbus Input Discrete TableThe Modbus Input Discrete table is mapped exclusively to the CPU Discrete Input (%I) table.Applicable Functions▪ Read Input DiscretesModbus Coil TableThe Modbus Coil table is mapped exclusively to the CPU Discrete Output (%Q) table.Applicable Functions▪ Read Coils▪ Write Coils▪ Write Single CoilAddress ConfigurationAddress mapping is done in the Machine Edition Hardware Configuration of the CPU. All Ethernet modules anddaughter-boards in the PLC use Modbus-to-PLC address mapping based on this one map. The Modbus/TCPServer does not use COMMREQs to configure address mapping.Each PLC memory area is mapped to an appropriate Modbus address space. On the Settings tab, ModbusAddress Space Mapping can be set to Standard Modbus Addressing or Disabled. If Modbus Address SpaceMapping is set to Standard, the Modbus/TCP Address Map tab displays the standard reference assignments.Number Modbus Register Start Address End Address PLC Memory Address Length1 0xxxx – Coil Table 1 32768 %Q00001 327682 1xxxx Discrete Table 1 32768 %I00001 327683 3xxxx Input Registers 1 64 %AI00001 644 4xxxx – Register Table 1 1024 %R00001 10245 6yxxx – Internal Table 0 0 %W0001 0When Modbus Address Space Mapping is set to Disabled on the Settings tab, the Modbus/TCP Address Map tabdoes not appear.
