Danfoss VLT HVAC Drive FC 100 Series, Руководство по конструкции

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confirming the action taken, any data to be returned and
an error-checking field. If an error occurs in receipt of the
message, or if the slave is unable to perform the requested
action, the slave will construct an error message, and send
it in response, or a timeout occurs.
7.6.4 Adjustable Frequency Drive with
Modbus RTU
The Adjustable frequency drive communicates in Modbus
RTU format over the built-in RS-485 interface. Modbus RTU
provides access to the control word and bus reference of
the Adjustable frequency drive.
The control word allows the Modbus master to control
several important functions of the Adjustable frequency
drive:
•
Start
•
Stop of the Adjustable frequency drive in various
ways:
Coast stop
Quick stop
DC Brake stop
Normal (ramp) stop
•
Reset after a fault trip
•
Run at a variety of preset speeds
•
Run in reverse
•
Change the active set-up
•
Control the adjustable frequency drive’s built-in
relay
The bus reference is commonly used for speed control. It is
also possible to access the parameters, read their values,
and where possible, write values to them. This permits a
range of control options, including controlling the setpoint
of the Adjustable frequency drive when its internal PI
controller is used.
7.7 Network Configuration
7.7.1 Adjustable Frequency Drive with
Modbus RTU
To enable Modbus RTU on the Adjustable frequency drive,
set the following parameters
Parameter Setting
8-30 Protocol Modbus RTU
8-31 Address 1 - 247
8-32 Baud Rate 2400 - 115200
8-33 Parity / Stop Bits Even parity, 1 stop bit (default)
Table 7.10
7.8 Modbus RTU Message Framing
Structure
7.8.1 Adjustable Frequency Drive with
Modbus RTU
The controllers are set up to communicate on the Modbus
network using RTU (Remote Terminal Unit) mode, with
each byte in a message containing two 4-bit hexadecimal
characters. The format for each byte is shown in
Table 7.11 .
Start
bit Data byte Stop/
parity
Stop
Table 7.11
Coding System 8-bit binary, hexadecimal 0-9, A-F. 2
hexadecimal characters contained in each 8-
bit field of the message
Bits Per Byte 1 start bit
8 data bits, least significant bit sent first
1 bit for even/odd parity; no bit for no
parity
1 stop bit if parity is used; 2 bits if no parity
Error Check Field Cyclical Redundancy Check (CRC)
Table 7.12
RS-485 Installation and Set...
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HVAC Drive Design Guide
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