Modbus Communication; Overview Of Modbus Rtu And Tcp Communication - Siemens SIMATIC S7 System Manual

10. Set the baud rate of the RS-485 serial interface:
11. Enter the Slave address.
Each drive (a maximum of 31) can be operated over the bus.
12. Set the serial link timeout.
This is the maximum permissible period between two incoming data
telegrams. This feature is used to turn off the inverter in the event of a
communications failure. Timing starts after a valid data telegram has been
received. If a further data telegram is not received within the specified time
period, the inverter will trip and display fault code F0070. Setting the value to
zero switches off the control.
13. Transfer the data from RAM to EEPROM:
12.5

Modbus communication

12.5.1

Overview of Modbus RTU and TCP communication

Modbus function codes
● A CPU operating as a Modbus RTU master (or Modbus TCP client) can read/write both
● A CPU operating as a Modbus RTU slave (or Modbus TCP server) allows a supervisory
Table 12- 45 Read data functions: Read remote I/O and program data
Modbus function code
01
02
03
04
S7-1200 Programmable controller
System Manual, 11/2011, A5E02486680-05
data and I/O states in a remote Modbus RTU slave (or Modbus TCP server). Remote
data can be read and processed in the user program.
device to read/write both data and I/O states in a remote CPU. The supervisor device can
write new values in remote CPU memory that can be processed in the user program.
Read slave (server) functions - standard addressing
Read output bits: 1 to 2000 bits per request
Read input bits: 1 to 2000 bits per request
Read Holding registers: 1 to 125 words per request
Read input words: 1 to 125 words per request
105BCommunication processor
12.5 Modbus communication
P2010 Index 0= 4 (2400 baud)
5 (4800 baud)
6 (9600 baud)
7 (19200 baud
8 (38400 baud)
9 (57600 baud)
12 (115200 baud)
P2011 Index 0=(0 to 31)
P2014 Index 0=(0 to 65,535 ms)
0=timeout disabled
P0971=1 (Start transfer) Save the changes
to the parameter settings to EEPROM
581