7.3.2 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 filter 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).
STX
LGE
ADR
DATA
BCC
195NA099.10
7.3.3 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
LGE = 4 + 1 + 1 = 6 bytes
The length of telegrams with 12 data bytes is
LGE = 12 + 1 + 1 = 14 bytes
The length of telegrams containing texts is
10
1)
+n bytes
1)
The 10 represents the fixed characters, while the “n’” is variable (depending on the length of the text).
7.3.4 Filter Address (ADR)
Two different address formats are used.
The address range of the filter 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 = Filter address 1-31
2. Address format 1-126:
Bit 7 = 1 (address format 1-126 active)
Bit 0-6 = Filter address 1-126
Bit 0-6 = 0 Broadcast
The slave returns the address byte unchanged to the master in the response telegram.
7.3.5 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.
7.3.6 The Data Field
The structure of data blocks depends on the type of
telegram. There are three telegram types, and the type
applies for both control telegrams (master=>slave) and
response telegrams (slave=>master).
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