Acyclic Read/Write Request Sequence; Data Structure In The Acyclic Telegrams - Danfoss VLT Profinet MCA 120 Operating Instructions Manual

PROFINET Acyclic Communicat...

7.4 Acyclic Read/Write Request Sequence

A Read or Write service on a frequency converter
parameter takes place as illustrated in Illustration 7.2.
Illustration 7.2 Acyclic Read/Write Request Sequence
A Read or Write on a frequency converter parameter must
be initiated by an acyclic write service on slot 0, index 47.
If this Write request is valid, a positive write response
without data is returned from the frequency converter
immediately. If not, a negative write response is returned
from the frequency converter.
The frequency converter now interprets the "Profidrive
parameter channel" part of the Data Unit, and start to
perform this command internal in the frequency converter.
As the next step, the master sends a Read request. If the
frequency converter is still busy performing the internal
parameter request, a negative response without data is
returned from the frequency converter. This request is
repeated by the master, until the frequency converter has
the response data ready for the frequency converter
parameter request.
The following example shows the details of the telegrams
needed for the Read/Write service.
MG90U302
Operating Instructions

7.5 Data Structure in the Acyclic Telegrams

The data structure for a write/read parameter request,
consists of three main blocks:
•
•
•
Arrange according to Table 7.1:
Word number
1 Header
2 Header
3 (Param. 1)
4 (Param. 1)
5 (Param. 1)
6 (Param. 2)
7 (Param. 2)
8 (Param. 2)
9 (Param. 3)
10 (Param. 3)
11 (Param. 3)
....
N (Data Param. 1)
N+1 (Data Param. 1)
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Header block
Parameter block
Data block
Request #
Axis
Attribute
Parameter number
Subindex number
Attribute
Parameter number
Subindex number
Attribute
Parameter number
Subindex number
Format
Data
7
Request ID
# Param.
# elements
# elements
# elements
# elements
Data
39
7