Modbus Communication; Modbus Rtu Communication; Modbus Rtu - General; Supported Data Transfer Rates For Rtu - Siemens SIMOCODE pro Function Manual

2.3

Modbus communication

2.3.1

Modbus RTU communication

2.3.1.1

Modbus RTU - general

Modbus RTU (Remote Terminal Unit) is a standard protocol for network communication and
uses the electrical RS485 connection for serial data transmission between Modbus devices
in the network.
Modbus RTU uses a master/slave network in which the entire communication is triggered by
only one master device while the slaves can only respond to the request of the master. The
master sends a request to a slave address and only this slave address responds to the
command (exception: broadcast frames to slave address 0 which are not acknowledged by
the slaves).
2.3.1.2

Supported data transfer rates for RTU

SIMOCODE pro supports the following data transfer rates in Modbus RTU mode:
● 300 baud
● 600 baud
● 1,200 baud
● 2,400 baud
● 4,800 baud
● 9,600 baud
● 19,200 baud (default setting)
● 57,600 baud.
2.3.1.3

Assignment of SIMOCODE data to Modbus addresses with Modbus RTU

All SIRIUS data are available in datasets or in the process image:
● System datasets
● Datasets specific to a device subfamily
● Product-specific datasets.
To be addressable via Modbus, the data in these datasets or in this process image are
converted to Modbus data formats.
Data access to
Read-only bits
Read/write bits
Read-only datasets and words (16-bit)
Read/write datasets and words
1 coil corresponds to 1 bit.
1 register corresponds to 1 word (2 bytes).
SIMOCODE pro - Communication
Function Manual, 11/2018, A5E40508495002A/RS-AC/003
2.3 Modbus communication
Data type according to Modbus nomenclature
Discrete inputs
Coils
Input registers
Holding registers
Communication
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