Profibus-DP

5 Cyclic data channel set-upThe Profibus-DP data window contains four 16-bit words for input and four16-bit words for output data. The first input and output words are reservedfor non-cyclic parameter access and therefore cannot be used as cyclic datachannels. The mapping of the six remaining words (three input and threeoutput) can be programmed to any Unidrive or Mentor II parameter, or UD70virtual parameter. The mapping cannot be changed dynamically, as a resetof the UD70 or MD24 must be performed to make the changes active.On Mentor II, the internal values of the real parameters have a higherresolution than the display values. Therefore, when writing a value to aMentor II real parameter, the value must be multiplied by 16 before beingconverted to hexadecimal.Example. to write a value of 1000 (0x03E8) to #1.18, the actual value thatmust be transmitted via the Profibus-DP network is 0x3E80.This also permits higher resolution on the speed loop. To write a value of235.5 to #1.18, transmit 0xEB8 to the Mentor II. Although this fraction willnot be shown on the display, the internal values in the Mentor II will use thisextra resolution.5.1 Parameter mappingThe following diagram illustrates the concept of programmable mappingwith Unidrive parameter #20.PP controlling the mapping.UnidriveParameterSetCyclicDataChannelFor example the following diagram illustrates the mapping process onUnidrive.Profibus–DPIssue code: pbnu2 11