Siemens MindConnect Nano System Manual page 70

Configuring protocols
4.5 Overview of Modbus RTU protocol for MindConnect Nano
Example
Example
Reading the first Holding Register, number
40001, has the Data Address 0.
VariableType: 4 or 3 (unsigned short or
short)Reading the second Input Register,
number 30002, has the Data Address 1.
Reading a float (32 bits) from Input Register
30108 / 30109, has the Data Address 107.
Reading a string. This example describes to
read four letters from register 400006 and
400007. Each register contains two
characters.
Using Modbus register addresses directly
Usually, it is necessary to enter Modbus registered address decremented by 1 as "start address",
but it may lead to confusion when comparing the data point's "start address" with the registered
address from Modbus device's manual. Therefore, enter a negative value in the "response
address offset" field to directly use the registered address from the Modbus device's manual as
"start address". In case a negative value has been entered as "response address offset", this value
will internally be subtracted from the given "start address" number to read the data from
Modbus device. Positive "response address offset" values will be handled to address specific data
within the read data if several registers need to be read to acquire the data from Modbus device
as data block and the necessary data itself is only a part of that data block.
Supported since:
MindConnect Nano V03.04.03.03 b001
Samples:
Registered address from Modbus
device manual
Start address
MindConnect Nano
System Manual 7/2023
Data Function
Data Function
type type
type type
Read
int Holding
Registers
Read
Input
int
Registers
1
Read
double Input
Registers
Read
string Holding
Registers
Using decremented Using address
start address from manual
303 303
302 303
Response
Response
Start Variable
Start Variable
Address
Address
address type
address type
Offset
Offset
unsigned
0 short or 0
short
unsigned
short or 0 1
short
float
(reads
107 0
two
registers)
unsigned
5 0
short
Getting data from a read
data block
64001
1)
64001
Response
Response
Quantity
Quantity
1
1
2
(registers)
70