Functions And Properties For Modbus Rtu Master - Siemens SICAM Q200 7KG97 Manual

Communication Modbus

2.2 Functions and Properties for Modbus RTU Master

2.2

Functions and Properties for Modbus RTU Master

Supported Modbus Register Sets
•
Coil status registers (0x references, read only)
•
Input status registers (1x references, read only)
•
Input registers (3x references, read only)
•
Holding registers (4x references, read only)
Supported Modbus Functions
The Modbus RTU Master of SICAM Q200 supports the following Modbus functions:
Table 2-2
Function
Number
01 (0x01H)
02 (0x02H)
03 (0x03H)
04 (0x04H)
Support of Modbus Slave Devices
The Modbus RTU master supports 16 Modbus slave devices each with:
•
15 readable measured values per Modbus slave device
•
6 readable indications from each Modbus slave device
NOTE
i i
If more than the specified number of measured values and/or indications have to be read by a Modbus
slave device, it is possible to assign the same address to multiple devices when configuring the devices
connected to the Modbus master in SICAM Q200. The data of all devices with the same address are then
queried by a Modbus slave device.
Properties of the Modbus RTU Master
•
Master-Slave protocol
•
The individual data bytes in the messages are transmitted asynchronously with 11 bits:
1 start bit,
8 data bits,
1 parity bit and 1 stop bit or
No parity bit and 2 stop bits
•
Single messages are separated by bus silent intervals of at least 3.5 character times and end with a CRC
code for error detection.
•
RS485 is used as interface.
16
Supported Modbus RTU Master Functions
Function Name
Read Coil Status
Read Discrete Inputs (Read Input
Status)
Read Holding Registers
Read Input Registers
Description
Reading one or several coil status registers of a
Modbus slave
Reading one or several input status registers of a
Modbus slave
Reading one or several holding registers of a Modbus
slave
Reading one or several input registers of a Modbus
slave
SICAM, Multifunctional Recorder, Manual
E50417-C1040-C606-A3, Edition 03.2017