Danfoss VLT 3000 Series Product Manual page 74

Serial data interface
Group 5..
(continued)
74
Group description
Byte 1:
Start byte which in this case must be the
character "<" (ASCII: 60).
Bytes 2 and 3:
The two-digit address of the frequency
converter with which communication is
required. This address is also programmed
in parameter 500.
Sending to address 00 means broadcast
to all units connected to the bus. None of
the units will reply, but they will carry out the
command.
Byte 4:
Control parameter telling the VLT
frequency converter what to do with the
following data values.
U (update) means that the data value
(bytes 13-19) must be read into the
frequency converter's parameter (bytes
9-13).
R (read) means that the master wants to
read the data value of the parameter
stated in bytes 9-12.
C (control) means that the frequency con-
verter reads only the four command bytes
(5-8) and returns with status. Parameter
number and data value will be ignored.
I (read index) means that the frequency
converter reads index and parameter, and
returns with status.
Parameter is stated in bytes 9-12 and
index is stated in bytes 13-18.
Parameters with indices are read-only
parameters. Action will be taken on the con-
trol word.
Two-dimensional indices (x,y) (parameters
601 and 602) are separated by a comma,
see byte 19.
Example:
Index = x, y
Data value = 013,05
Byte 14-18 = 013 05
Byte 19 = 2
®
MG.30.A7.02 - VLT is a registered Danfoss trademark
Bytes 5-8:
Control and status words are used to send
commands to the frequency converter and
to send status from frequency converter to
master.
Bytes 9-12:
In these bytes the parameter number is set.
Bytes 13:
Used for the sign before data value in
bytes 14-18. All characters other than "−"
are taken as "+".
Bytes 14-18:
Here is placed the data value of the para-
®
meter stated in bytes 9-12.
The value must be a whole number. If a
decimal point is needed it is stated in byte
19.
Note: Some data values have square brack-
ets with a number, e.g. [0]. Use this number
instead of the "text" data value.
Bytes 19:
The position of the decimal point in the data
value stated in bytes 14-18. The number
states the number of characters after the
decimal point.
Byte 19 can then be 0, 1, 2, 3, 4 or 5.
For example, the number 23.75 is stated:
Byte no.
ASCII character +
If byte 19 = 9 in the response telegram see
table page 80.
Bytes 20, 21:
Used for counter control from byte 2 up to
and including 19. The decimal values of the
ASCII characters are added and reduced to
the two "low" characters, e.g. Σ 235 [ ]
reduced = 35. If no control is necessary can-
cel the function with "?" (ASCII: 63) in the
two bytes.
Byte 22:
Stop byte stating the end of the telegram.
The character ">" is used (ASCII: 62).
13 14 15 16 17 18 19
2 3 7 5 0 3