LS Industrial Systems iS7 RAPIEnet, Option Manual

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iS7 Ethernet Option Manual
15
Protocol Data Unit (PDU)
This is the practical data of the Modbus TCP consists of Function Code
and Data.
Details will be described in the “(2) description on the Function Code”
below.
(2) Function Code Description
Modbus TCP is divided into Client and Server. The Client gives
command and the Server responses to the command. Generally,
Clients can be PLC, HMI, or PC and the Server is the inverter.
① ① ① ①
Read Holding Registers
The function used to read the data in the Inverter (Server).
Constitution of the frame requested from Client to Server;
Constitution of the frame sent from Server to Master in response;
Requested Frame Length Value
Function code 1 Bytes 0x03
Comm. address 2 Bytes 0x0000 ~ 0xFFFF
The number of
data requested
2 Bytes
1~16
(LSIS Inverter standard)
Response Frame Length Value
Function code 1 Bytes 0x03
Comm. address 1 Bytes
2 x The requested
number of data
The number of
data requested
The requested
number of data x 2
Bytes
Value of the data of the
given number from the
communication address