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7.3 Network Configuration
To enable the FC protocol for the frequency converter, set
the following parameters.
Parameter
Setting
Parameter 8-30 Protocol
FC
Parameter 8-31 Address
1–126
Parameter 8-32 Baud
Rate
2400–115200
Parameter 8-33 Parity /
Stop Bits
Even parity, 1 stop bit (default)
Table 7.3 Parameters to Enable the Protocol
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. 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
3
2
4
5
6
7
195NA036.10
Start
bit
Even Stop
Parity bit
Illustration 7.4 Content of a 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).
Several data bytes (variable, depending on the type of
telegram) follow.
A data control byte (BCC) completes the telegram.
STX
LGE
ADR
DATA
BCC
195NA099.10
Illustration 7.5 Telegram Structure
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.
4 data bytes
LGE=4+1+1=6 bytes
12 data bytes
LGE=12+1+1=14 bytes
Telegrams containing texts
10
1)
+n bytes
Table 7.4 Length of Telegrams
1) The 10 is the fixed characters, while the n is variable (depending
on the length of the text).
7.4.4 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.
7.4.5 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.
RS485 Installation and Set-...
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Compressor Drive CDS 803
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