Example:
writing to frequency converter address 22 (16H) with address format
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 CheckSum
(BCS) is 0.
When the first byte (02H) has been received:
BCS = BCC EXOR “first byte”
(EXOR = exclusive-or)
BCS
= 0 0 0 0 0 0 0 0 (00 H)
EXOR
1. byte
= 0 0 0 0 0 0 1 0 (02H)
BCC
= 0 0 0 0 0 0 1 0 (02H)
Each subsequent byte gates with BCS EXOR and produces a new BCC,
e.g.:
BCS
= 0 0 0 0 0 0 1 0 (02H)
EXOR
2nd byte
= 1 1 0 1 0 1 1 0 (D6H)
BCC
= 1 1 0 1 0 1 0 0 (D4H)
4.7.4 Data Character (Byte)
The structure of data blocks depends on the type of telegram. There are
three types of telegram, and the type of telegram applies for both control
telegrams (masterslave) and response telegrams (slavemaster). The
three types of telegram are:
-
Parameter block, used to transfer parameters between master
and slave. The data block is made up of 12 bytes (6 words) and
also contains the process block.
-
The process block is made up of a data block of four bytes (2
words) and contains:
-
Control word and reference value
-
Status word and present output frequency (from slave
to master)
-
Text block, which is used to read or write texts via the data
block.
Parameter commands and responses (AK).
Bits no. 12-15 are used to transfer parameter commands from master to
slave and the slave's processed responses back to the master.
4 Programming
VLT
®
Decentral FCD 300 Design Guide
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MG.90.S1.02 - VLT
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is a registered Danfoss trademark
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