VLT
®
2800 Series
Programming
Telegram length (LGE)
The telegram length is the number of data bytes plus
theaddressbyteADRplusthedatacontrolbyteBCC.
The length of telegrams with 4 data bytes is:
LGE=4+1+1=6bytes
The length of telegrams with 12 data bytes is:
LGE=12+1+1=14bytes
The length of telegrams c ontaining texts is 10+n bytes.
10 represents the fixed characters, while the ’n’ is
variable (depending on the length of the text).
F
requency converter a ddress (ADR)
Two d ifferent address formats are used, w ith
the frequency converter’s address range being
either 1-31 or 1-126.
1. Address format 1-31
The byte for address range 1-31 has the
following profile:
Bit 7 = 0 (address format 1-31 a ctive)
Bit 6 is not used
Bit 5 = 1: Broadcast, address bits ( 0-4) are not used
Bit 5 = 0: N o Broadcast
Bit 0-4 = Frequency converter address 1-3 1
2. Address format 1-126
The byte for address range 1 - 126 has
the following profile:
Bit 7 = 1 (address format 1-126 act ive)
Bit 0-6 = Frequency converter address 1-126
Bit 0-6 = 0 Broadcast
The slave sends the address byte back unchanged
in the response telegram to the master.
E
xample:
writing to frequency converter address 22 (16H)
with address fo rmat 1-31:
Data control byte ( BCC)
The data control byte is explained in this example:
Before the first byte in the telegram is received,
the Calculated Che ckSum (BCS) is 0.
When the first byte (02H) has been received:
BCS = BCC EXOR "first byte"
(EXOR = exclusive-or)
BCS =00000000(00H)
EXOR
1. byte =00000010(02H)
BCC =00000010(02H)
Each subsequent byte gates w ith B CS EXOR
and produces a new BCC, e.g.:
BCS =00000010(02H)
EXOR
2ndbyte =11010110(D6H)
BCC =11010100(D4H)
MG.28.E9.02 - VLT is a registered Danfoss trademark
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