7.4.3 Message Length (LGE)
The message length is the number of data bytes plus the address byte ADR and the data control byte BCC.
The length of messages with 4 data bytes is LGE = 4 + 1 + 1 = 6 bytes
The length of messages with 12 data bytes is LGE = 12 + 1 + 1 = 14 bytes
The length of messages 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).
7.4.4 Adjustable Frequency Drive Address (ADR)
Two different address formats are used.
The address range of the adjustable frequency drive 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 = Adjustable frequency drive address 1-31
2. Address format 1-126:
Bit 7 = 1 (address format 1-126 active)
Bit 0-6 = Adjustable frequency drive 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.
7 RS-485 Installation and Set-up
VLT AQUA Low Harmonic Drive Instruction
Manual
7-6
MG.20.T1.22 - VLT
®
is a registered Danfoss trademark
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