ECOLAB Versatronic Modbus Beschreibung Seite 118

Modbus protocol description
3.4.1 Reading n words
This function is used to read n words, starting from a specific address.
Data request
Slave address
1 byte
Response
Slave address
1 byte
Example
Reading the IP address of the device. The address used in the example is 10.10.1.69.
Since each octet of the IP address is saved in a word, it is necessary here to read
4 words, that is, 8 bytes.
For these and other Modbus addresses, see
on page 41.
Hex code for the data query:
01
Slave
Hex code for the response (values in byte format):
01 03
Slave Function
3.4.2 Writing one word
The data blocks for the instruction and response are identical when writing a word.
CAUTION!
Write operations in some R/W parameters result in them being saved in the
EEPROM or flash memory. These memory modules have only a limited
number of write cycles (approx. 100,000 or 10,000).
Thus, frequent writing of certain variables can result in a memory error.
The number of write operations should therefore be kept as low as possible. Write
operations can also be carried out using 'external analog inputs' . 'External analog inputs'
are not saved in the EEPROM or flash memory, and are suitable for fast write cycles.
Instruction
Slave address
1 byte
417102397 Rev. 1-10.2019
Function
Address of first word Number of words x
0x03 oder 0x04
1 byte 2 bytes
Funktionscode Number of bytes
0x03 or 0x04 read
1 byte 1 byte
03 19 C9
Function address 1st word
08 00 0A
bytes read 10
Function 0x06 Word address
1 byte 2 bytes
18
2 bytes
Word value(s)
2 x bytes
Ä Chapter 8 'Modbus address tables'
00 04
Number of words
00 0A 00 01
10 1
IP address
Word value
2 bytes
Checksum CRC
2 bytes
Checksum CRC
2 bytes
93 6B
CRC
00 45 37 E5
69 CRC
Checksum CRC
2 bytes