Danfoss VLT FCD 303 Operating Instructions Manual page 87

It is possible to change the direction of rotation via the
serial reference. This is done by converting the binary
reference value to 2' complement. See example.
Example - Control word and serial communication ref.:
The frequency converter is to recei v e a start
command and the reference is to be set to 50%
(2000 Hex) of the reference range.
Control word = 047F Hex ⇒ Start command.
Reference = 2000 Hex ⇒ 50% reference.
The frequency converter is to recei v e a start
command and the reference is to be set to -50%
(-2000 Hex) of the reference range.
The reference value is first converted to 1' complement,
and then 1 is added binarily to obtain 2' complement:
2000 Hex
1' complement
2' complement
Control word = 047F Hex ⇒ Start command.
Reference = E000 Hex ⇒ -50% reference.
Present output frequency
The value of the frequency converter's present output
frequency is transferred as a 16-bit word. The value is
transferred as whole numbers 0 - ±32767 (±200%).
16384 (4000 Hex) corresponds to 100%.
Output frequency has the following format:
0-16384 (4000 Hex) 0-100% (Par. 201
Output frequency low limit - Par. 202 Output
frequency high limit).
MG.04.B7.02 - VLT is a registered Danfoss trademark
0010 0000 0000 0000 0000
1101 1111 1111 1111 1111
+ 1
1110 0000 0000 0000 0000
®
VLT FCD Series
Example - Status word and current output frequency:
The master recei v es a status message from the
frequency converter that the current output frequency
is 50% of the output frequency range.
Par. 201 Output frequency low limit = 0 Hz
Par. 202 Output frequency high limit = 50 Hz
Status word = 0F03 Hex.
Output frequency = 2000 Hex ⇒ 50% of the
frequency range, corresponding to 25 Hz.
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