Modbus process image in the memory of the COM461MT
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COM461MT_D00011_00_M_XXEN/05.2013
7.3.3
Reference value on channel 2
The following reference value is stored in this channel: 12.34 A
Tab. 7.5: Reference data stored in channel 2
7.3.4
Explanation of how to access floating point values
The test value 12.34 can be read out via Modbus/TCP using Modbus function
4 at the address 0x0014. The test value has a size of 2 words.
Proceed as follows:
1. Determine the correct byte offset
Interpreting both words as unsigned integer values should result in the
following values:
Word 1 with address 0x14: unsigned integer value => 16709 (0x4145)
Word 2 with address 0x15: unsigned integer value => 28836 (0x70A4)
2. Determine the correct byte or word swap
There are four different combinations of swapping. The only correct
value is 12.34.
All swapping combinations are represented in the following table.
Word 0x14
0x15
0x16
0x17
HiByte
LoByte
HiByte
LoByte
HiByte
LoByte
HiByte
LoByte
0x41
0x45
0x70
0xA4
0x00
0x03
0x00
0x4A
Floating point value (Float)
AT&T
R&U
Description
12.34
No/No Ampere
Overcurrent
