Network Configuration; Fc Protocol Message Framing Structure; Content Of A Character (Byte); Telegram Structure - Danfoss VLT AutomationDrive FC 301 Design Manual

RS-485 Installation and Set...
The master function cannot be transferred to another node
(single-master system).
The physical layer is RS-485, thus utilising the RS-485 port
built into the frequency converter. The FC protocol
supports different telegram formats:
•
A short format of 8 bytes for process data
•
A long format of 16 bytes that also includes a
parameter channel
•
A format used for texts

12.6 Network Configuration

12.6.1 Frequency Converter Set-up
Set the following parameters to enable the FC protocol for
the frequency converter.
Parameter Number
8-30 Protocol
8-31 Address
8-32 FC Port Baud Rate
8-33 Parity / Stop Bits
Table 12.2 FC Protocol Parameters
12.7 FC Protocol Message Framing
Structure

12.7.1 Content of a Character (byte)

12 12
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. This bit is set at "1"
when it reaches parity. Parity is when there is an equal
number of 1s in the 8 data bits and the parity bit in total.
A stop bit completes a character, thus consisting of 11 bits
in all.
Start 0
bit
Illustration 12.5 Content of a Character

12.7.2 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)
178
Setting
FC
1-126
2400-115200
Even parity, 1 stop bit (default)
1 2 3 4 5 6
®
VLT AutomationDrive FC 301/FC 302 Design Guide, 0.25-75 kW
A number of data bytes (variable, depending on the type
of telegram) follows.
A data control byte (BCC) completes the telegram.
STX
Illustration 12.6 Telegram Structure

12.7.3 Telegram Length (LGE)

The telegram length is the number of data bytes plus the
address byte ADR and the data control byte BCC.
4 data bytes
12 data bytes
Telegramscontaining texts
Table 12.3 Length of Telegrams
1) The 10 represents the fixed characters, while the "n'" is variable
(depending on the length of the text).

12.7.4 Frequency Converter Address (ADR)

2 different address formats are used.
The address range of the frequency converter is either 1-31
or 1-126.
1. Address format 1-31:
2. Address format 1-126:
7 Even Stop
Parity bit
The follower returns the address byte unchanged to the
master in the response telegram.

12.7.5 Data Control Byte (BCC)

The checksum is calculated as an XOR-function. Before the
first byte in the telegram is received, the Calculated
Checksum is 0.
MG33BF02 - Rev. 2013-12-20
LGE ADR DATA
LGE=4+1+1=6 bytes
LGE=12+1+1=14 bytes
1)
10 +n bytes
Bit 7 = 0 (address format 1-31 active)
Bit 6 is not used
Bit 5 = 1: Broadcast, address bits (0-4) are not
used
Bit 5 = 0: No Broadcast
Bit 0-4 = frequency converter address 1-31
Bit 7 = 1 (address format 1-126 active)
Bit 0-6 = frequency converter address 1-126
Bit 0-6 = 0 Broadcast
BCC