•
•
•
•
•
•
•
•
12 data bytes
LGE=12+1+1=14 bytes
Telegrams containing texts
10
(1)
+n bytes
1
The 10 represents the fixed characters, while the n is variable (depending on the length of the text).
8.4.4 Drive Address (ADR)
Address format 1–126:
Bit 7 = 1 (address format 1–126 active).
Bit 0–6 = drive address 1–126.
Bit 0–6 = 0 broadcast.
The follower returns the address byte unchanged to the master in the response telegram.
8.4.5 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.
8.4.6 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->follower) and response telegrams (follower->master).
The 3 types of telegram are:
Process block (PCD).
Parameter block.
Text block.
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 follower).
Status word and present output frequency (from follower to master).
STX
LGE
ADR
PCD1
PCD2
BCC
e
3
0
b
a
2
6
9
.1
0
Illustration 69: Process Block
Parameter block
The parameter block is used to transfer parameters between master and follower. The data block is made up of 12 bytes (6 words)
and also contains the process block.
e3
0b
a2
71
.1
0
STX
LGE
ADR
PCD1
PCD2
BCC
PKE
IND
PWE
PWEhigh
low
Illustration 70: Parameter Block
Text block
The text block is used to read or write texts via the data block.
e
3
0
b
a
2
7
0
.1
0
STX
LGE
ADR
PCD1
PCD2
BCC
PKE
IND
Ch1
Ch2
Chn
Illustration 71: Text Block
AJ363928382091en-000101 / 130R0983
106 | Danfoss A/S © 2021.04
RS485 Installation and Set-up
VLT® Flow Drive FC 111
Design Guide