A stop bit completes a character, thus consisting of 11 bits
in all.
0
1
3
2
4
5
6
7
195NA036.10
Start
bit
Even Stop
Parity bit
Illustration 3.2 Content of a Character
3.4.2 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
DATA
BCC
195NA099.10
Illustration 3.3 Telegram Structure
3.4.3 Telegram Length (LGE)
The telegram length is the number of data bytes plus the
address byte ADR and the data control byte BCC.
4 data bytes
LGE=4+1+1=6 bytes
12 data bytes
LGE=12+1+1=14 bytes
Telegramscontaining texts
10
1)
+n bytes
Table 3.4 Length of Telegrams
1)
The 10 represents the fixed characters, while the “n’” is variable
(depending on the length of the text).
3.4.4 Frequency Converter Address (ADR)
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.
3.4.5 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.
RS-485 Installation and Set...
VLT
®
AutomationDrive FC 360 Design Guide
MG06B202 - VLT
®
is a registered Danfoss trademark
43
3
3