Fc Protocol Message Framing Structure - Fc; Content Of A Character (Byte); Telegram Structure; Length (Lge) - Danfoss VLT AutomationDrive Design Manual

RS-485 Installation and Set...
11.6 FC Protocol Message Framing
Structure - FC 300

11.6.1 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. 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 1 2 3 4
bit

11.6.2 Telegram Structure

Each telegram has the following structure:
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).

11.6.4 Frequency Converter Address (ADR)

Two different address formats are used.
The address range of the frequency converter is either 1-31
or 1-126.
1. Address format 1-31:
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
2. Address format 1-126:
Bit 7 = 1 (address format 1-126 active)
Bit 0-6 = frequency converter address 1-126
Bit 0-6 = 0 Broadcast
The slave returns the address byte unchanged to the
master in the response telegram.
FC 300 Design Guide
5 6 7 Even Stop
Parity bit
®
MG.33.BD.02 - VLT is a registered Danfoss trademark
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

11.6.3 Length (LGE)

The length is the number of data bytes plus the address
byte ADR and the data control byte BCC.

11.6.5 Data Control Byte (BCC)

The checksum is calculated as an XOR-function. Before the
first byte in the is received, the Calculated Checksum is 0.

11.6.6 The Data Field

The structure of data blocks depends on the type of .
There are three types, and the type applies for both
control telegrams (master=>slave) and response telegrams
(slave=>master).
The 3 types of are:
DATA BCC
LGE = 4 + 1 + 1 = 6 bytes
LGE = 12 + 1 + 1 = 14 bytes
1)
10 +n bytes
257
11 11