ICP DAS USA I-7242D User Manual page 107

Here is an example of correspondences for a full frame, based on the
"Read Holding Registers" Command (0x03).
Element under Utility
Modbus Devices Address
Modbus Device I/O Type
query Register Address
Communication Words
Element under Gateway
Modbus Devices Address
Device I/O Type
Modbus
response
I-7242D DeviceNet/Modbus RTU Gateway User's Manual, July 2006, Version 1.1
Byte count
Data
I-7242D user manual
Modbus frame fields
Device no.
Function no.
st
No. 1 word (MSB/LSB)
No. of words (MSB/LSB)
Modbus frame fields
Device no.
Function no.
No. of bytes read
st
Value of 1 word (MSB/LSB)
...............................
Value of last word (MSB/LSB)
Size
(byte)
1
1
2
2
Size
(byte)
1
1
1
2
...
2
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