COM462RTU_D00010_04_M_XXDE / 06.2021 31
COMTRAXX® COM462RTU
6.3.4 Explanation of how to access floating point values
The test value 12.34 can be read out via Modbus RTU using Modbus function 0x03 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 resp. 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.
Hex value
sequence
Word 1
Word 2
Floating
point value
Byte 1
Byte 2
Byte 3
Byte 4
CORRECT
A
41
B
45
C
70
D
A4
12.34
Word
swapping
C
70
D
A4
A
41
B
45
4.066E+29
Byte
swapping
B
45
A
41
D
A4
C
70
3098.27
Word and byte
swapping
D
A4
C
70
B
45
A
41
-5.21E-17
6.4
Channel descriptions for the process image
Value
Measured value description
alarm message
operating message
Note
0
1 (0x01)
Insulation fault
2 (0x02)
Overload
3 (0x03)
Overtemperature
4 (0x04)
Failure line 1
5 (0x05)
Failure line 2
6 (0x06)
Insul. OP light
Insulation fault operating theatre light
7 (0x07)
8 (0x08)
Failure distribution board
9 (0x09)
Failure oxygen
