Chapter 8. Modbus/TCP Server136 PACSystems* RX7i & RX3i TCP/IP Ethernet Communications User Manual GFK-2224Qtables for Modbus data. The following table shows how each Modbus table is mapped to the PACSystemsreference tables.Modbus Reference TablesModbus FileAccess(6xxxx)Modbus HoldingRegister Table(4xxxx)Modbus InputRegister Table(3xxxx)Modbus InputDiscrete Table(1xxxx)Modbus CoilTable(0xxxx)PACSystemsReference Tables--- --- --- 1 – 32768(bits)--- %I1 – 32768(bits)--- --- 1 – 32640(16-bit words)--- --- %AI1 – 32640(16-bit words)--- --- --- --- 1 – 32768(bits)%Q1 – 32768(bits)--- 1 – 32640(16-bit words)--- --- --- %R1 – 32640(16-bit words)F1,R1 –F525,R2880(16-bit words)--- --- --- --- %W1 –5,242,880(16-bit words)Modbus File Access TableThe Modbus File Access table is mapped exclusively to PACSystems %W memory.Applicable Functions▪ Read File Record▪ Write File RecordTranslating %W Reference AddressesTo find the PACSystems %W memory address equivalent of a Modbus File and Record:%W = 10,000 (F-1) + RTo find the Modbus File and Record equivalent of a PACSystems %W memory address:File = W-110,000 + 1Record = W – (10,000 (F – 1))(Discard any fractional portion;round the result downward tothe next integer value).Figure 53: Calculations for Modbus File and Record %W Memory AddressCautionIf you use the Modbus function Write File Record, and specify multiple recordsections, the first N-1 sections will be written to the server’s PLC referencememory, even if an error prevents the writing of the last section.
