User Manual

DI[D-SE-0029872.1.4] EtherNet/IP Communications Support
EIO0000001601 Draft 2013/07/17 67
Modbus Object (Class ID 0x44)
Modbus Object (Class ID 0x44)
Introduction
The Modbus object is assigned a vendor-specific class ID of 68 (0x44). The Modbus object is an
application object that provides the read/write requests of the Smart Antenna memory zones. For
the Smart Antenna Modbus object:
” The class code is 0x44 (68).
” The single supported instance is 1.
Instance Services
The Modbus object supports these instance services:
Service Code 0x4E Description
The table describes the service parameters of the read holding registers request:
1
The request parameter is little indian. The Modbus protocol is big endian. You may have to swap
bytes depending on the Modbus subsystem implementation.
The table describes the service parameters of the read holding registers response:
1
The data is returned as 16-bit entities for each register. The actual data type of the values is
unknown.
2
The response data is little indian. The Modbus protocol is big endian. You may have to swap bytes
depending on the Modbus subsystem implementation.
Service Code Name Description
0x4E Read holding registers This service sends a read request of the specified registers (123 words
maximum).
0x50 Write holding registers This service sends a write requests of the specified registers (123
words maximum).
Name Data Type Description Semantics of Values
Starting address UINT
Offset in table to begin reading from
1
Zero based
Quantity of holding registers UINT
Number of holding registers to read
1
(Max
number = 123)
-
Name Data Type Description Semantics of Values
Holding register values
Array of 16-bit word
1
Holding register values read
2
-