Functions
5.11 Operation in fieldbus systems
Frequency inverter
Operating Instructions, 08.10. 2008, t.b.d.
183
Parameter value (PWE) third and fourth word
When data is transferred via PROFIBUS or PROFINET, the parameter value (PWE) is
transferred as a double word (32 bit). Only one parameter value can be transferred in a
single message frame.
A 32 bit parameter value includes PWE1 (high-order word, third word) and PWE2 (low-order
word, fourth word).
A 16 bit parameter value is transferred in PWE2 (low-order word, fourth word). In this case,
PWE1 (high-order word, third word) must be set to 0 in the PROFIBUS DP master /
PROFINET I/O controller.
Note
When communication takes place via USS, the word length can be configured in P2013. For
more information, see "Communication via USS".
Rules for editing requests/responses
● A request or a response can only be referred to one parameter.
● The master must constantly repeat a request until it receives a suitable response.
● The master recognizes the response to a request that it sent by:
– Evaluating the response identifier
– Evaluating the parameter number (PNU)
– Evaluating the parameter index (IND), if necessary, or
– Evaluating the parameter value PWE, if necessary.
● The complete request must be sent in a telegram. Request telegrams cannot be
subdivided. The same applies to responses.
● If response telegrams contain parameter values, the drive always returns the current
parameter value when it repeats response telegrams.
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