GE PACSystems RX7i, User Manual

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Chapter 9. Modbus/TCP Client
160 PACSystems* RX7i & RX3i TCP/IP Ethernet Communications User Manual GFK-2224Q
(Word 9) Modbus Function Code: Word 9 specifies Function Code 23, Read/Write Multiple Register.
(Word 10) Local PLC Memory Type (Write With Data Read From Server): Words 10–12 specify the location in
the local PLC where the Ethernet interface will write data received from the remote server. Values for Word 10
are listed on page 150. The value 8 specifies Register Memory %R.
(Word 11) Local PLC Starting Address LSW (Write With Data Read From Server): Word 11 determines the
least significant word (LSW) of the starting address in the local PLC from which the data is to be written. The
value entered is the offset (1-based) from the beginning of PLC memory for the memory type and mode
specified in Word 10. This offset will be either in bits, bytes, or words depending on the mode specified. Valid
ranges of values depend on the PLC’s memory ranges.
(Word 12) Local PLC Starting Address MSW (Write With Data Read From Server): Word 12 determines the
most significant word (MSW) of the starting address in the local PLC from which the data is to be written. This
value will typically be 0 unless the address is above 65535 for %W memory.
(Word 13) Remote Device Read Address: Word 13 specifies the register(s) to read from the remote
Modbus/TCP device.
(Word 14) Number Registers to Read From Remote Device: Words 14 specifies the quantity of registers to
read from the remote device.
(Word 15) Local PLC Memory Type (Read Data to Write to Server): Words 15–17 specify the location in the
local PLC where the Ethernet interface will read data to use for writing to the remote server. Values for Word
15 are listed on page 150. The value 8 specifies Register Memory %R.
(Word 16) Local PLC Starting Address LSW (Read Data to Write to Server): Word 16 determines the least
significant word (LSW) of the starting address in the local PLC from which the data is to be read. The value
entered is the offset (1-based) from the beginning of PLC memory for the memory type and mode specified in
Word 15. This offset will be either in bits, bytes, or words depending on the mode specified. Valid ranges of
values depend on the PLC’s memory ranges.
(Word 17) Local PLC Starting Address MSW (Read Data to Write to Server): Word 17 determines the most
significant word (MSW) of the starting address in the local PLC from which the data is to be read. This value will
typically be 0 unless the address is above 65535 for %W memory.
(Word 18) Remote Device Write Address: Word 18 specifies the register(s) to be written on the remote
Modbus/TCP device.
(Word 19) Number Registers to Write To Remote Device: Words 19 specifies the quantity of registers to write
to the remote device.
(Word 20) Unit Identifier: This field is typically used by Ethernet to Serial bridges to specify the address of a
Modbus Slave on a multi-drop link. The Modbus/TCP Unit Identifier is a special control code used in a
Modbus/TCP message block.