Functions
8.7 Communication via USS
Control Units CU240S
Operating Instructions, 11/2006, A5E00766042B AA
8-27
The length of the PKW channel is determined by parameter P2013, that for the process data
by parameter P2012. If either no PKW or no PZD is required, the corresponding parameters
can be set to zero ("PKW only" or "PZD only" respectively). It is not possible to transmit
"PKW only" and "PZD only" alternatively. If both channels are required they must be
transferred together.
8.7.3 Process data channel (PZD)
Description
In this area of the telegram, process data (PZD) are continually exchanged between the
master and slaves. Dependent of the direction the process data channel contains data for a
request to the USS slaves or for a response to the USS master. In the requests are control
words and setpoints for the slaves and in the responses are status words and actual values
for the master.
67: +6: 67:
3
=6: +,: =6:
3
3
3=' 3=' 3=' 3=' 3='
3='
3=' 3=' 3=' 3='
5HVSRQVH
WR866PDVWHU
5HTXHVW
WR866VODYH
Figure 8-19 Process data channel
The number of PZD words in a USS-telegram are determined by parameter P2012, where
the first two words are:
● Control word 1(STW1) and main setpoint (HSW)
● Status word 1 (ZSW1) and actual value (HIW)
If P2012 is greater or equal to 4 the additional control word (STW2) is transferred as the 4
th
PZD word (default setting).
The sources of all other PZDs are defined with parameter P2019 for a RS485 interface and
P2016 for a RS232 interface.
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