Example For Addressing A Data Point - Siemens SENTRON 7KN POWERCENTER 3000 Manual

Functions
5.9 Modbus devices
Byte ordering with big-endian data transmission
Register
Register address
Register address + 1
Number of registers
Storage of the time stamp according to the Unix format Time_T, seconds since January 1,
1970
Note
If the attributes of a data point are not set completely and correctly, errors can occur in
individual services of the 7KN Powercenter 3000.
For that reason, we recommend creating a Modbus device in full and in detail, testing it and
copying this Modbus device multiple times within the project with copy and paste or
exchanging it between projects with "Export device(s)" and "Import device(s)".
5.9.1.1

Example for addressing a data point

As from register address 6001, 2 registers, i.e. 4 bytes, are to be read.
In byte 2 (offset = 2, because counted 0, 1, 2, 3), bits 4 and 5 are to be read.
Element Example
Register 6001
address
Register 2
count
Byte offset 2
Byte count 1
Bit offset 4
Bit count 2
84
U8
High byte 0x00
Low byte Data byte
High byte -
Low byte -
1
0 1
<---------------------------------------- 1 byte --------------------------------------------------->
7 6
7 6
U16
High data byte
Low data byte
-
-
1
Bit or byte field
Register
Register +1
Byte 2
5 Bit 4 3
Bit 5 Bit 4
3
Equipment Manual, 07/2020, L1V30579222003-03
U32 FP32
1st data byte 1st data byte (sign
2nd data byte 2nd data byte
3rd data byte 3rd data byte
4th data byte 4th data byte
2
2 1 0
2 1 0
7KN POWERCENTER 3000
bit)
2
3