Data Types - ECOLAB Versatronic Modbus Beschreibung

Modbus protocol description
3.5

Data types

Data type Description
Low byte of a word as an integer value; the high byte is not
used.
Value ranges:
Byte
n
n
Word (16 bit) as integer value
Value ranges:
Word
n
n
2 words as 32-bit floating-point number with coding to IEEE
754, where it must be kept in mind that bytes 1 and 2 are
interchanged with bytes 3 and 4 during transmission.
S = Sign bit
E = Exponent (two's complement)
M = 23-bit normalized mantissa
IEEE 754 standard coding
Byte 1
SEEEE
EEE
Modbus coding of floating-point variables in the Versatronic
1. Address of the 1st Modbus register
Floating
for variables
point
Byte 3
MMMMMMMM
When creating customer-specific applications, the correct
byte sequence in storage format needs to be checked.
Many compilers use the following storage format:
Compiler coding
Byte 4
MMMM
MMMM
Adress x
Double word (32-bit) as unsigned integer value
Uint32
Value range: 0 to 4.294.967.295
Character string for up to 20 Unicode characters in UTF-8
coding with up to 3 bytes per character
The character string thus consists of up to 60 bytes. Each of
Char[60]
the 30 Modbus register words contains 2 successive bytes
of the character string.
Note that the character string must always have "\0" (ASCII
code 0x00) as the terminating code.
Least significant bit in a word as bit value
Bool
0000 0000 0000 0001 = 1 or TRUE
0000 0000 0000 0000 = 0 or FALSE
417102397 Rev. 1-10.2019
0 to 255 for unsigned data
128 to 127 for signed data
0 to 65535 for unsigned data
-32768 to 32767 for signed data
Byte 2 Byte 3
EMMMMMMM MMMMMMMM
Byte 4
MMMMMMMM
Byte 3 Byte 2 Byte 1
MMMM EMMM
SEEEEEEE
MMMM MMMM
Adress Adress
Adress x+3
x+1 x+2
Access
read only
read/ write 03, 04, 06,
read only
read/ write 03, 04, 06,
read only
Byte 4
MMMM
MMMM
Address of the
2nd Modbus
register for
read/ write 03, 04, 16
variables
Byte 1 Byte 2
SEEEE EMMM
EEE MMMM
read only
read/ write 03, 04, 16
read only
read/ write
read only
read/ write 03, 04, 06,
20
Possible Number
Function Modbus
codes register
03, 04
1
16
03, 04
1
16
03, 04
2
03, 04
2
03, 04
30
03, 04, 06,
16
03, 04
1
16