GE Industrial Solutions 6KCV301PDP33 Profibus - DP Bus for AV300i - Manual (Page 13)

3
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—————— BYTE ASSIGNMENT ——————
Profibus-DP
3.0 BYTES ASSIGNMENT FOR DATA EXCHANGE
The 6KCV301PDP33 card uses a 16-byte frame. The first 8 bytes represent the
configuration channel for the acyclic data exchange, the other 8 are the process
data channel for the cyclic exchange.
The bytes assignment is as follows:
Configuration channel Process data channel
WORD 0 WORD 1 WORD 2 WORD 3 0 1 2 3 4 5 6 7
Data / error
Subindex / Type
Index
Control byte
As to the Data/Error and Index fields, the data format is arranged from the
least to the most significant byte. The meaning of the fields is the following:
A ) Data frame from Master to Slave:
1 ) Data / Error
The content of this field depends on the kind of service carried out: in
case of writing it contains the parameter value, in case of reading it has no
meaning.
2 ) Subindex/Type
It contains the parameter subindex, if any. If the parameter has no
subindexes it has to be set to 0. For parameters with subindex, this has to
be set from 1 to the max. number of parameter elements; the value 0 is not
accepted and rejected. It is not possible to read the whole object, but only
its single elements. In case of service carried out towards the DGF option,
this field should contain the data type (see DGF manual).
3 ) Index
Index of the parameter involved in the operation with format low byte -
high byte.
4 ) Control byte
The meaning of this byte is described in 3.1.