Telegram Length (Lge); Frequency Converter Address (Adr); Data Control Byte (Bcc); The Data Field - Danfoss VLT AutomationDrive FC 300 Operating Instructions Manual

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A number of data bytes (variable, depending on the type
of telegram) follows.
A data control byte (BCC) completes the telegram.
STX LGE
Illustration 7.5

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.
7 7
Data
4 data bytes
12 data bytes
Telegrams containing texts
Table 7.3
1)
The 10 represents the fixed characters, while the "n'" is variable
(depending on the length of the text).

7.3.4 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:
Bit 7 = 0 (address format 1-31 active)
Bit 6 is not used
STX LGE
Illustration 7.6
Parameter block
The parameter block is used to transfer parameters
between master and slave. The data block is made up of
12 bytes (6 words) and also contains the process block.
STX LGE
Illustration 7.7
134
VLT Automation Low Harmonic Drive Operating Instructions
ADR DATA
Length
LGE = 4 + 1 + 1 = 6 bytes
LGE = 12 + 1 + 1 = 14 bytes
10 1) +n bytes
ADR
ADR PKE IND
MG34O202 - VLT
2. Address format 1-126:
BCC
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).
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:
-
-
PCD1
PWE PWE
high low
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Bit 5 = 1: Broadcast, address bits (0-4) are not
used
Bit 5 = 0: No Broadcast
Bit 0-4 = frequency converter address 1-31
Bit 7 = 1 (address format 1-126 active)
Bit 0-6 = frequency converter address 1-126
Bit 0-6 = 0 Broadcast
Control word and reference value (from master to
slave)
Status word and present output frequency (from
slave to master)
PCD2
PCD1 PCD2
BCC
BCC