FCM 300 Series
MG.03.B6.2G - VLT is a registered Danfoss trademark
VLT address (ADR)
Two different address formats are used:
1. Siemens USS protocol address format:
7
6
5
4
3
2
1
0
0
0
0
0
0
Bit 7 = 0
Bit 6 is not used
Bit 5 = 1:
Broadcast, address bits (0-4) are not used
Bit 5 = 0: No Broadcast
Bits 0-4 = VLT address 1-31
2. Danfoss format:
7
6
5
4
3
2
1
0
1
1
1
1
1
Bit 7 = 1
Bits 0-6 = VLT address 1-127 (0 = Broadcast)
Data control byte (BCC)
The data control byte can best be explained by
means of an example: Before the first sign of the
telegram is received, BCC = 0.
7
6
5
4
3
2
1
0
BCC
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
After the first sign has been received:
BCC
NEW
= BCC
OLD
EXOR "first byte"
(EXOR = exclusive-or gate)
BCC
OLD
= 0 0 0 0 0 0 0 0
EXOR
"first byte"
= 0 0 0 0 0 0 1 0 (02H)
BCC
NEW
= 0 0 0 0 0 0 1 0
Each additional, subsequent byte is gated by
BCC
OLD
EXOR and gives a new BCC
NEW
, e.g.:
BCC
OLD
= 0 0 0 0 0 0 1 0
EXOR
"second byte" = 1 1 0 1 0 1 1 0 (D6H)
BCC
NEW
= 1 1 0 1 0 1 0 0
The result after the last received sign is BCC.
■
Databytes
The block of databytes is divided into two smaller
blocks:
1. Parameter bytes used for transferred parameters
between leader and follower
2. Process bytes, covering
- Control word and reference value
(from leader to follower)
- Status word and present output frequency
(from follower to leader)
This structure applies to both the control telegram
(leader
→
follower) and the reply telegram
(follower
→
leader).
Parameter bytes
Process bytes
PKE
IND
PWE
HIGH
PWE
LOW
PCD1
PCD2
00 00 00 00 00 00 00 00 00 00 00 00
There are two types of telegrams:
-
with 12 bytes built up as shown above, with
parameter and process block
-
with four bytes, which is the process block from
the 12 byte telegram
1. Parameter bytes
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
Commands and replies (AK)
Bits no. 12-15 are used for transmitting commands
from leader to follower and the follower's processed
reply back to the leader.
PNU
PKE
AK
Commands
and replies
Parameter
number
Not in use
IND
PWE
HIGH
PWE
LOW
Serial communication
15-4
