Telegram Length (Lge); Frequency Converter Address (Adr); Data Control Byte (Bcc); The Data Field - Danfoss VLT HVAC Drive FC 102 Design Manual

Installation and Set-up

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.
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).

7.4.4 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:
a. Bit 7 = 0 (address format 1-31 active)
7 7
b. Bit 6 is not used
c. Bit 5 = 1: Broadcast, address bits (0-4) are not used
d. Bit 5 = 0: No Broadcast
e. Bit 0-4 = frequency converter address 1-31
2. Address format 1-126:
a. Bit 7 = 1 (address format 1-126 active)
b. Bit 0-6 = frequency converter address 1-126
c. 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.

7.4.6 The Data Field

The structure of data blocks depends on the type of telegram. There are 3 telegram types, and the type applies for both
control telegrams (master=>slave) and response telegrams (slave=>master).
The 3 types of telegram are:
Process block (PCD)
The PCD is made up of a data block of 4 bytes (2 words) and contains:
•
Control word and reference value (from master to slave)
•
Status word and present output frequency (from slave to master)
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Design Guide
Danfoss A/S © Rev. 05/2014 All rights reserved.
LGE = 4 + 1 + 1 = 6 bytes
LGE = 12 + 1 + 1 = 14 bytes
1)
10 +n bytes
MG16C202