Comtrol IOLM Modbus TCP - Manual (Page 6)

8 - Chapter 1. Modbus/TCP Interface IO-Link Master Modbus/TCP Reference Manual: 2000590 Rev. A
Modbus Function Codes
1.1. Modbus Function Codes
This table shows the supported Modbus function codes.
1.2. Modbus Address Definitions
The address definitions for Modbus/TCP interface are shown in the following table.
Message Type Function Code Maximum Message Size
Read Holding Registers 3 250 Bytes (125 Words)
Write Single Register 6 2 bytes (1 Word)
Write Multiple Registers 16 (10 hex) 246 Bytes (123 Words)
Read/Write Holder Registers 23 (17 hex)
Write: 242 bytes (121 Words
Read: 246 bytes (123 Words)
IO-Link Port
1
IO-Link Port
2
IO-Link Port
3
IO-Link Port
4
Access Length
Multiple
Port PDI
Data
Block(s)
999 (Base 0)
1000 (Base 1)
1999 (Base 0)
2000 (Base 1)
2999 (Base 0)
3000 (Base 1)
3999 (Base 0)
4000 (Base 1)
Read-
Only
Configurable
per port (s)
Port
Specific
PDI Data
Block
1000 (Base 0)
1001 (Base 1)
2000 (Base 0)
2001 (Base 1)
3000 (Base 0)
3001 (Base 1)
4000 (Base 0)
4001 (Base 1)
Read-
Only
Configurable
per port
Multiple
Port PDO
Data
Block(s)
1049 (Base 0)
1050 (Base 1)
2049 (Base 0)
2050 (Base 1)
3049 (Base 0)
3050 (Base 1)
4049 (Base 0)
4050 (Base 1)
Read/
Write Configurable
per port(s)
Port
Specific
PDO Data
Block
1050 (Base 0)
1051 (Base 1)
2050 (Base 0)
2051 (Base 1)
3050 (Base 0)
3051 (Base 1)
4050 (Base 0)
4051 (Base 1)
Read/
Write Configurable
per port
Receive
SPDU
Response
1100 (Base 0)
1101 (Base 1)
2100 (Base 0)
2101 (Base 1)
3100 (Base 0)
3101 (Base 1)
4100 (Base 0)
4101 (Base 1)
Read-
Only
4 to 125 Words
Transmit
SPDU
Request
1300 (Base 0)
1301 (Base 1)
2300 (Base 0)
2301 (Base 1)
3300 (Base 0)
3301 (Base 1)
4300 (Base 0)
4301 (Base 1)
Write-
Only
4 to 123 Words
Port Information Block (Continuous Block) 232 Words
Vendor
Name
1500 (Base 0)
1501 (Base 1)
2500 (Base 0)
2501 (Base 1)
3500 (Base 0)
3501 (Base 1)
4500 (Base 0)
4501 (Base 1)
Read-
Only
64 Chars
32 Words