Danfoss FCM305 56 Instruction Manual page 98

VLT address (ADR)
Two different address formats are used:
1. Siemens USS protocol address format:
7 6 5 4
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
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
BCC
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
After the first sign has been received:
BCC = BCC EXOR "first byte"
NEW OLD
BCC = 0 0 0 0 0 0 0 0
OLD
EXOR
"first byte" = 0 0 0 0 0 0 1 0 (02H)
BCC = 0 0 0 0 0 0 1 0
NEW
Each additional, subsequent byte is gated by
BCC EXOR and gives a new BCC
OLD
BCC = 0 0 0 0 0 0 1 0
OLD
EXOR
"second byte" = 1 1 0 1 0 1 1 0 (D6H)
BCC = 1 1 0 1 0 1 0 0
NEW
The result after the last received sign is BCC.
15-4
3 2 1 0
3 2 1 0
4 3 2 1 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
(EXOR = exclusive-or gate)
, e.g.:
NEW
FCM 300 Series
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
PKE IND PWE
HIGH
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
PKE
AK
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.
MG.03.B6.2G - VLT is a registered Danfoss trademark
Process bytes
PWE PCD1 PCD2
LOW
IND PWE PWE
HIGH LOW
PNU