Danfoss VLT Series Design Manual page 139

VLT ® HVAC Drive Design Guide
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The bus reference is commonly used for speed control. It is also possible to access the parameters,
read their values, and where possible, write values to them. This permits a range of control op-
tions, including controlling the setpoint of the adjustable frequency drive when its internal PID
controller is used.
7.3. Network Configuration
7.3.1. VLT HVAC Adjustable Frequency Drive Set-up
Set the following parameters to enable the FC protocol for the VLT HVAC.
Parameter Number
8-30
8-31
8-32
8-33
7.4. FC Protocol Message Framing Structure
7.4.1. Content of a Character (byte)
Each character transferred begins with a start bit. Then 8 data bits are transferred, corresponding
to a byte. Each character is secured via a parity bit, which is set at "1" when it reaches parity (i.e.,
when there is an equal number of 1's in the 8 data bits and the parity bit in total). A character is
completed by a stop bit, thus consisting of 11 bits in all.
Change of the active set-up
Control of the two relays built into the adjustable frequency drive
Parameter name
Protocol
Address
Baud Rate
Parity/Stop bits
MG.11.B4.22 - VLT ® is a registered Danfoss trademark.
7. RS-485 Installation and Set-up
Setting
FC
1 - 126
2400 - 115200
Even parity, 1 stop bit (default)
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