I/O Modules • 151
Process Data Architecture for MODBUS/TCP
WAGO-I/O-SYSTEM 750
Linux Fieldbus Coupler
7.2.3 Analog Input Modules
The hardware of an analog input module has 16 bits of measured analog
data per channel and 8 bits of control/status. However, the
coupler/controller with MODBUS/TCP does not have access to the 8
control/status bits. Therefore, the coupler/controller with MODBUS/TCP
can only access the 16 bits of analog data per channel, which are grouped
as words and mapped in Intel format in the Input Process Image.
When digital input modules are also present in the node, the analog input
data is always mapped into the Input Process Image in front of the digital
data.
1 Channel Analog Input Module
750-491, (and all variations)
Input Process Image
Byte Destination
Offset
High Byte
Low Byte
Remark
0 D1 D0
Measured
Value
U
D
1 D3 D2
Measured
Value
U
ref
2 Channel Analog Input Modules
750-452, -454, -456, -461, -462, -465, -466, -467, -469, -472, -474, -475,
-476, -477, -478, -479, -480, -481, -483, -485, -492, (and all variations),
753-452, -454, -456, -461, -465, -466, -467, -469, -472, -474, -475, -476, -
477, -478, -479, -483, -492, (and all variations)
Input Process Image
Byte Destination
Offset
High Byte
Low Byte
Remark
0
D1
D0
Measured Value Channel 1
1
D3
D2
Measured Value Channel 2