Standard isdu request command format – Comtrol IO-Link Master EIP-4 User Manual
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IO-Link Master EtherNet/IP Reference Manual: 2000589 Rev. A
Chapter 2. Functionality Descriptions - 25
ISDU Request Message Format-From PLC to IO-Link Master
2.2.2. ISDU Request Message Format-From PLC to IO-Link Master
Write and read ISDU commands have the same message data format. Each ISDU request message is
comprised of one or more commands. The command(s) can consist of either a series of nested commands or a
single read command.
Note: A list of nested ISDU commands is terminated with either a control field of 0, (single/last operation), or
the end of the message data.
2.2.2.1. Standard ISDU Request Command Format
This table displays a standard ISDU request command format with ControlLogix PLCs.
Name
Data Type
Parameter Descriptions
Byte Swapping
USINT
Bits 0-3:
0= No byte swapping.
1= 16-bit (INT) byte swapping of ISDU data.
2= 32-bit (DINT) byte swapping of ISDU data.
Bits 4-7:
Set to zero. Unused.
RdWrControlType
USINT
Provides the control and type of ISDU command.
Bits 0-3, Type Field:
0 = NOP (No operation)
1 = Read operation
2 = Write operation
3 = Read/Write “OR”
4 = Read/Write “AND”
Bits 4-7, Control Field:
0 = Single/Last Operation (length can vary from to 1 to 232)
1 = Nested batch command – fixed 4 byte data area
2 = Nested batch command – fixed 8 byte data area
3 = Nested batch command – fixed 16 byte data area
4 = Nested batch command – fixed 32 byte data area
5 = Nested batch command – fixed 64 byte data area
6 = Nested batch command – fixed 128 byte data area
7 = Nested batch command – fixed 232 byte data area
Index
UINT
The parameter address of the data object in the IO-Link device.
Subindex
UINT
The data element address of a structured parameter of the data
object in the IO-Link device.
Datalength
UINT
Length of data to read or write.
For nested batch commands, the data length can vary from 1 to
the fixed data area size.
Data
Array of
USINTs,
UINTs, or
UDINTs.
Size of array is determined by the Control field in
RdWrControlType.
Note: Data is valid only for write commands.