NORD Drivesystems BU2200 - Manual (Page 18)

4 Communication and Protocol
18 BU 2200 GB-3813
4.2.4 Setpoint (SW) and Actual Value (IW)
The functions of the setpoint and the actual value are assigned via frequency inverter parameters:
Type Relevant parameter
Setpoint P546 … P548
Actual value P543 … P545
The following three kinds of data transfer are possible:
Percentage transfer
The process value is transferred as an integer with a value range of -32768 to 32767 (8000 hex to
7FFF hex). The value 16384 (4000 HEX) corresponds to 100 %. The value -16384 (C000 hex) is
equal to -100 %.
For frequencies, the 100 % value corresponds to the FI parameter "Maximum Frequency" (P105) and
for currents, this is the FI parameter "Torque Current Limit" (P112) Frequencies and currents result
from the following formulae.
16384
105 P Value
Frequency


16384
112 P Value
Current


"Value" represents the 16Bit actual or setpoint value transmitted via the bus
Binary transmission
Inputs and outputs, as well as Digital In bits and Bus Out bits are processed bit-by-bit.
Transmission of positions
In the FI, positions have a value range of +/- 50000.000 rotations. A motor rotation can be divided into
a maximum of 1000 steps. This scaling is independent of the encoder which is used.
The 32 Bit value range is divided into a Low word and a High word, so that 2 setpoints or actual values
are required for the transfer. It does not matter which 2 words (except for the 1st word) are used for
this.
Direction of
transmission
Transmitted data (12 Byte)
1st word 2nd word 3rd word 4th word 5th word 6th word
Busmaster 
bus module
Control word 32 bit setpoint Setpoint 3 Setpoint 4 Setpoint 5
Busmaster 
bus module
Status word Actual value
1 32 bit actual value Actual value
4 Actual value
5
Table 8: Depiction of 32Bit setpoint/actual values
It is also possible to only transmit the Low component of the position. This results in a limited value
range from +32,767 to -32,768 rotations. This value range can be extended with the aid of the gear
ratio factor (P607 & P608). However, it must be noted that there is an according reduction in the
resolution.
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