JUMO mTRON T Manual page 31

Data request:
05
Slave
Response:
05
Slave
The value of the read out bits is 02
NOTE!
If the bits are not to be read out of a 32-bit field, but rather from a 16-bit field, it is not neces-
sary to add 10
Example with the data type bit field 64
The objective is to read out the state of the digital variables 1 to 54 of the multifunction panel.
Its Modbus address here in the example is 7.
According to Chapter 7.3.1 "Modbus addresses for each HMI module", page 94, the word ad-
dress for this is 0x0002. It contains the values in bits 0 to 53:
Hexadecimal calculation of the bit address for
Bit address = (0x0002 × 0x10) + 0x0
Hexadecimal calculation of the bit address for
Since it is a 64-bit field, 64 values in the example are to be read starting with the address 20
Data request:
07
Slave
Response:
07
Slave
As is also the case in the example with the data type bit field 32, the bit values are not directly
read out of the data response without detecting the exact assignment.
A bit field 64 consists of 4 words each with 16 bits. The word with the highest value is always
transmitted first, followed by the word with the next-highest value and so on until the lowest val-
01
Function
01
Function
or 16 , since there is no preceding high word.
Hex Dec
the first bit of the bit field
Result: 0x20
the last bit of the bit field
Bit address = 0x20 + 0x40
Result: 60
01
Function Address of 1st
01
Function
3 Modbus protocol description
00 31 00 02
01 02
Bytes Bit value
(= 2 = 10 ): bit 0 = 0 and bit 1 = 1
Hex Dec Bin
Decimal calculation of the bit address for the
Decimal calculation of the bit address for the
00 20 00 40
Number of bit
bit
08 10 00
Bytes
read
ED 80
CRC
D1 79
CRC
first bit of the bit field
Bit address = (2 × 16) + 0
Result: 32
last bit of the bit field
Bit address = 32 + 64
Result: 96
56 3C
CRC
00 00 00 01 01 00
Bit values
.
Hex
C9 7B
CRC
31