Specifications

7.2.1 FC with Modbus RTU
The FC protocol provides access to the control word and
bus reference of the frequency converter.
The control word allows the Modbus master to control
several important functions of the frequency converter:
•
Start
•
Stop of the frequency converter 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 of the active set-up
•
Control of the two relays built into the frequency
converter
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 frequency converter when its internal PID controller
is used.
7.3 Network Configuration
7.3.1 Frequency Converter Set-up
Set the following parameters to enable the FC protocol for
the frequency converter.
Parameter Number Setting
O-30 Protocol
FC
O-31 Address
1 - 126
O-32 Drive Port Baud Rate
2400 - 115200
O-33 Drive Port Parity
Even parity, 1 stop bit (default)
Table 7.3 FC Protocol Parameters
7.4 FC Protocol Message Framing Structure
7.4.1 Content of a Character (byte)
Each character transferred begins with a start bit. Eight
data bits are transferred, corresponding to a byte. Each
character is secured via a parity bit. This bit is set at "1"
when it reaches parity. Parity is when there is an equal
number of 1’s in the 8 data bits and the parity bit in total.
A stop bit completes a character, thus consisting of 11 bits
in all.
0 1 32 4 5 67
195NA036.10
Start
bit
Even Stop
Parity bit
Illustration 7.5 Example Character
7.4.2 Telegram Structure
Each telegram has the following structure:
1. Start character (STX)=02 Hex
2. A byte denoting the telegram length (LGE)
3. A byte denoting the frequency converter address
(ADR)
A number of data bytes (variable, depending on the type
of telegram) follows.
A data control byte (BCC) completes the telegram.
STX LGE ADR DATABCC
195NA099.10
Illustration 7.6 Example Telegram
Installation and Set-up VLT® HVAC Drive FC 102 Design Guide
164 MG16C102 - Rev. 2013-08-20
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