Issue Number: 3
25
6 Non
Cyclic
Data
The non-cyclic data channel provides a method for the master controller
to read from or write to any parameter within the Drive. This channel
can be used for single infrequent data transfers, or uploading and
downloading parameter sets to or from a particular node.
Non-cyclic data access to Unidrive parameters is controlled entirely by
the master controller program, and is not configured in any way when
the Profibus-DP network map is defined.
The Unidrive Profibus-DP interface currently provides the CT Single
Word Format of non-cyclic data. This mode is also available in the
Mentor II and Commander SE Profibus-DP interfaces.
NOTE
The non-cyclic data channel does not use decimal points. For
example, the digital speed reference 1 (#1.21) has units of Hertz,
accurate to 1 decimal place. To write a value of 24.6Hz to #1.21, the
value must be transmitted as 246.
6.1 CT
Single
Word
Format
The CT Single Word Format of non-cyclic data uses one word for non-
cyclic data. The non-cyclic sub-protocol requires a specific sequence of
4 words or "telegrams" to implement the parameter access. Each non-
cyclic word or telegram is split into 2 bytes to implement the sub-
protocol, with the high byte containing the control codes for each
telegram, and the low byte containing the data for each telegram.
b15 b14 b13 b12 b11 b10 b9 b8
R/W Error X
X
Stamp
number
b7 b6 b5 b4 b3 b2 b1 b0
Data byte
NOTE
If “little endian” data format has been selected, the bytes that form the
non-cyclic data word MUST be swapped BEFORE the non-cyclic data
word is transferred to the Profibus. See section 9.5.
