Danfoss VLT 8000 AQUA series Operating Instructions Manual page 150

Pause time, min.:
Response time, min.:
Response time, max.:
The time between individual characters in a telegram is
not to exceed 2 characters and the telegram must be
completed within 1.5 times the rated telegram time.
If the baudrate is 9600 kbaud and the telegram
length is 16 baud, the telegram must be
completed within 27.5 msec.
Telegram length (LGE)
Thetelegram length is the number of data bytes plus
address byte ADR plus data control byte BCC.
Telegrams with 4 data bytes have a length of:
LGE = 4 + 1 + 1 = 6 bytes
Telegrams with 12 data bytes have a length of:
LGE = 12 + 1 + 1 = 14 bytes
Telegrams that contain text have a length of 10+n
bytes. 10 is the fixed characters, while 'n' is variable
(depending on the length of the text).
Frequency converter address (ADR)
Two different address formats are used, in which
the address range of the frequency converter is
either from 1-31 or from 1-126.
1. Address format 1-31
The byte for this address range has the following profile:
Bit 7 = 0 (address format 1-31 active)
Bit 6 is not used
Bit 5 = 1: Broadcast, address bits (0-4), not used
Bit 5 = 0: No Broadcast
Bit 0-4 = frequency converter address 1-31
2. Address format 1-126
The byte for the 1-126 address range has
the following profile:
Bit 7 = 1 (address format 1-126 active)
Bit 0-6 = frequency converter address 1-126
150
2 characters
Bit 0-6 = 0 Broadcast
2 characters
20 msec.
The slave sends the address byte back to the master
in the reply telegram in unchanged form.
Example:
A telegram is sent to frequency converter address
22 using address format 1-31:
Data control byte (BCC)
The data control byte can be explained by means of
an example: Before the first byte of the telegram is
received, the calculated check sum (BCS) is 0.
After the first byte (02H) has been received:
BCS = BCC EXOR "first byte"
BCS
"first byte" =
BCC
Each additional, subsequent byte is gated with BCS
EXOR and results in a new BCC, such as:
BCS
"second byte" =
BCC
MG.83.A2.02 - VLT is a registered Danfoss trademark
®
VLT 8000 AQUA
(EXOR = exclusive-or gate)
= 0 0 0 0 0 0 0 0 (00H)
EXOR
0 0 0 0 0 0 1 0 (02H)
= 0 0 0 0 0 0 1 0
= 0 0 0 0 0 0 1 0 (02H)
EXOR
1 1 0 1 0 1 1 0 (D6H)
= 1 1 0 1 0 1 0 0