Network Configuration; Fc Protocol Message Framing Structure - Danfoss VLT AQUA Design Manual

7. RS-485 Installation and Set-up

7.3. Network Configuration

7.3.1. VLT AQUA Frequency Converter Set-up
Set the following parameters to enable the FC protocol for the VLT AQUA.
Parameter Number
8-30
8-31
8-32
8-33

7.4. FC Protocol Message Framing Structure

7.4.1. Content of a Character (byte)
Each character transferred begins with a start bit. Then 8 data bits are transferred, corresponding to a byte. Each character is secured via a parity bit,
which is set at "1" when it reaches parity (i.e. when there is an equal number of 1's in the 8 data bits and the parity bit in total). A character is completed
7
by a stop bit, thus consisting of 11 bits in all.
7.4.2. Telegram Structure
Each telegram begins with a start character (STX)=02 Hex, followed by a byte denoting the telegram length (LGE) and a byte denoting the frequency
converter address (ADR). A number of data bytes (variable, depending on the type of telegram) follows. The telegram is completed by a data control
byte (BCC).
7.4.3. Telegram Length (LGE)
The telegram length is the number of data bytes plus the address byte ADR and the data control byte BCC.
The length of telegrams with 4 data bytes is
The length of telegrams with 12 data bytes is
The length of telegrams containing texts is
1) The 10 represents the fixed characters, while the "n'" is variable (depending on the length of the text).
7.4.4. Frequency Converter Address (ADR)
Two different address formats are used.
130
Parameter name
Protocol
Address
Baud Rate
Parity/Stop bits
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MG.20.N3.02 - VLT is a registered Danfoss trademark
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VLT AQUA Drive Design Guide
Setting
FC
1 - 126
2400 - 115200
Even parity, 1 stop bit (default)
LGE = 4 + 1 + 1 = 6 bytes
LGE = 12 + 1 + 1 = 14 bytes
10 1) +n bytes