FCM 300 Series
MG.03.B6.02 - VLT is a registered Danfoss trademark
76
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 master and slave
2. Process bytes, covering
- Control word and reference value
(from master to slave)
- Status word and present output frequency
(from slave to master)
This structure applies to both the control telegram
(master
→
slave) and the reply telegram (slave
→
master).
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 master to slave and the slave's processed reply
back to the master.
PNU
PKE
AK
Commands
and r
eplies
Parameter
number
Not in use
IND
PWE
HIGH
PWE
LOW
Serial communication
