Fieldbus Specific Process Data Architecture For Modbus/Tcp - WAGO 750-341 Manual

46 • Fieldbus Coupler 750-341
Process image
3.1.4.3

Fieldbus specific Process Data Architecture for MODBUS/TCP

With some I/O modules, the structure of the process data is fieldbus specific.
In the case of an Ethernet TCP/IP coupler, the process image uses a word
structure (with word alignment). The internal mapping method for data greater
than one byte conforms to the Intel format.
The following section describes the process image for various WAGO-I/O-
SYSTEM 750 I/O modules when using an Ethernet TCP/IP coupler.
Note
Depending on the specific position of an I/O module in the fieldbus node, the
process data of all previous byte or bit-oriented modules must be taken into
account to determine its location in the process data map.
3.1.4.3.1 Digital Input Modules
Digital input modules supply one bit of data per channel to specify the signal
state for the corresponding channel. These bits are mapped into the Input
Process Image.
When analog input modules are also present in the node, the digital data is
always appended after the analog data in the Input Process Image, grouped
into bytes.
Some digital modules have an additional diagnostic bit per channel in the
Input Process Image. The diagnostic bit is used for detecting faults that occur
(e.g., wire breaks and/or short circuits).
1 Channel Digital Input Module with Diagnostics
750-435
Bit 7
2 Channel Digital Input Modules
750-400, -401, -405, -406, -410, -411, -412, -427, 438
Bit 7
Input Process Image
Bit 6 Bit 5 Bit 4
Input Process Image
Bit 6 Bit 5 Bit 4
Bit 3 Bit 2 Bit 1
Diagnostic
bit
S 1
Bit 3 Bit 2 Bit 1
Data bit
DI 2
Channel
WAGO-I/O-SYSTEM 750
Bit 0
Data bit
DI 1
Bit 0
Data bit
DI 1
Channel
2 1
ETHERNET TCP/IP