Transmission Formats (Integer, Float, Double, And Text Values) - JUMO mTRON T Manual

3.7 Transmission formats (integer, float, double, and text val-
ues)
Function 0x03 or 0x04 (reading n words) is used to read out integer, float, double, and text val-
ues.
Data request
Slave address
1 byte
Integer values are transmitted in the following format via Modbus:
first the high byte and then the low byte.
Response
Slave address
1 byte
3.7.1 Integer values
Example
In this example, the value of the integer variable 1 is to be read out at address 0x11F1 of the
central processing unit. The value here is to be "4" (word value 0x0004).
Data request:
01
Slave
Response (values in the Modbus float format):
01
Slave
Function
0x03 or 0x04
1 byte
Function
0x03 or 0x04
1 byte
03 11 F1
Function Address
of the 1st word
03 02
Function Bytes
read
3 Modbus protocol description
Address Number of words
of first word
2 bytes
Number Word value(s)
of bytes read
1 byte
00 01
Number of
words
00 04
Integer value
Checksum CRC
2 bytes 2 bytes
Checksum
CRC
x bytes 2 bytes
C5 D0
CRC
8D 19
CRC
37