Protocol Information - Siemens Sentron 7KN POWERCENTER 1000 Manual

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
U8
U16
U32
S16
UCHAR
FP32
FP64
TS
ST
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
Register address
Register address + 1
Number of registers
Circuit protection devices with communication and metering function
System Manual, 06/2021, L1V30827018B-01
U8
High byte 0x00
Low byte Data byte
High byte -
Low byte -
1
6.4 Modbus TCP connection
Description
unsigned 8 Bit
unsigned 16 Bit
unsigned 32 Bit
signed 16 Bit
unsigned Character with x Bytes
floating point 32 Bit (according to IEEE-754)
floating point 64 Bit (according to IEEE-754)
time stamp
system time - System time
U16 U32
High data byte 1st data byte
Low data byte 2nd data byte
- 3rd data byte
- 4th data byte
1 2
Functions
FP32
1st data byte
(sign bit)
2nd data byte
3rd data byte
4th data byte
2
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