Siemens Sentron 7KN POWERCENTER 1000 - Protocol Information

Functions
6.4 Modbus TCP connection
Circuit protection devices with communication and metering function
System Manual, 06/2021, L1V30827018B-01
63
See also
Messaging on TCP / IP Implementation Guide V1.0b
(https://www.modbus.org/docs/Modbus_Messaging_Implementation_Guide_V1_0b.pdf
)
Modbus Application Protocol Specification V1.1b
(https://modbus.org/docs/Modbus_Application_Protocol_V1_1b.pdf
)
6.4.2 Protocol information
Register addressing
According to the Modbus specification the registers are numbered starting from 1 but
addressed starting with 0. Subsequently, the start address in the protocol must be
decremented by -1 when reading out a register.
Function codes
Read processes (Read = R) are carried out alternatively with the function codes 0x03 or 0x04
according to the Modbus specification.
Write processes (Write = W) take place with function codes 0x06 or 0x10 according to the
Modbus specification.
Data formats
The following data formats are possible:
Abbreviation
Description
U8
unsigned 8 Bit
U16
unsigned 16 Bit
U32
unsigned 32 Bit
S16
signed 16 Bit
UCHAR
unsigned Character with x Bytes
FP32
floating point 32 Bit (according to IEEE-754)
FP64
floating point 64 Bit (according to IEEE-754)
TS
time stamp
ST
system time - System time
Storage of the time stamp according to the Unix format (UNIX_TS) in seconds since January
1, 1970
Byte arrangement with big-endian data transmission
Register
U8
U16
U32
FP32
Register address
High byte
0x00
High data byte
1st data byte
1st data byte
(sign bit)
Low byte
Data byte
Low data byte
2nd data byte
2nd data byte
Register address + 1
High byte
-
-
3rd data byte
3rd data byte
Low byte
-
-
4th data byte
4th data byte
Number of registers
1
1
2
2