ModbusTCP Process Image

The ModbusTCP process image makes a fundamental distinction between digital and byte-oriented (word-oriented) signals (Bus Terminals). Additionally, a distinction is made between inputs and outputs. The mapping table shows which Bus Terminals belong to which mapping.

At word-oriented access, first the analog and then the digital modules are listed in the address room.

Byte-oriented access

Digital inputs

Digital outputs

Offset 0 ... 4095
Modbus function
Reading 2
Writing: -

Offset 0 ... 4095
Modbus function
Reading 1
Writing5, 15

Word-oriented access

Analog/digital inputs

Analog/digital outputs

Offset 0x000 ... 0x0FF
Modbus function
Reading 3, 4, 23
Writing: -

Offset 0x800 ... 0x8FF
Modbus function
Reading 3,  23
Writing6, 16, 23

This will be clarified by example.

Example

IL2301-B900 (Remark: The IL2301-B900 has got 4 in- and 4 outputs on the module)
1 x IE1001
1 x IE2001

Inputs 

Outputs

Modbus function

Modbus Address/Offset

Fieldbus Box Module

Modbus function

Modbus Address/Offset

Fieldbus Box Module

3 read

0x0000

4 Bit IL2301

8 Bit IE1001

3 read

0x0800

4 Bit IL2301

8 Bit IE2001

4 read

0x0000

1 read

0x0000

2 read

0x0000 - 0x0001

5 write

0x0000-0x000B

 

 

 

15 write

0x0000-0x000B

 

 

 

6 write

0x800

 

 

 

16 write

0x800

 

 

 

23 write

0x800