Functions
5.11 Operation in fieldbus systems
Frequency inverter
152
Operating Instructions, 08.10. 2008, t.b.d.
5.11.1.1
User data range of the USS message frame
Structure of the user data
The user data range of the USS protocol is used to transfer application data. The process
data is exchanged cyclically between the converter and controller via the process data
channel (PZD), while the parameter channel is used for transferring parameter values
acyclically.
The following diagram shows the structure and sequence of parameter channel and process
data (PZD).
3.(
,1'
3:( 3:(
3:(P
3
3
3
3
3
Q
3.: 3.: 3.: 3.:
3.:P 3='
3='
3='\
67:
=6:
+6:
+,:
3
3
3='
3
3
3='
67:
=6:
3
3
3
3
3
3 YDULDEOHOHQJWK
3URFHVVGDWD3='
3.:3='VWUXFWXUH
'DWD%\WHV
3URWRFRO'DWD
3DUDPHWHUFKDQQHO3.:
3URWRFRO:RUGV
Figure 5-16 USS user data structure
The length of the parameter channel is defined via parameter P2013, while the length of the
process data is defined via parameter P2012. If neither a parameter channel nor process
data is required, the appropriate parameters can be set to zero ("PKW only" or "PZD only").
If both channels are required, they must be transferred together.
5.11.1.2
Data structure of the USS parameter channel
Description
The parameter channel is used to monitor and/or change parameters in the converter. Every
time data is transferred, the parameter ID and associated parameter value are sent. The
parameter channel can be set to a fixed length (3 or 4 data words) or variable length.
●
The first data word always contains the parameter ID (PKE)
●
The second data word contains the parameter index (IND)
●
The third and fourth data word contain parameter values, text, and descriptions (PWE)