Cyclic Process Data Exchange; Acyclic Data Exchange (Parameter Access) - Siemens SINAMICS G120 Manual

2 Solution
2.2 Description of the core functionality

Cyclic process data exchange

Process data is transferred cyclically, which means in each bus cycle, in order for it
to be transferred as quickly as possible.
The SIMATIC S7-300/400F transmits the control word and the setpoint value to
SINAMICS and receives the status word and the real value.
Depending on the message frame type, two further setpoint or real values, or
extended control or status words can be transferred respectively. The available
message frame types are listed in
instructions (/9/), for example.
In the SIMATIC S7-300/400F the process data is supplied as I/O input or
output words.
In the SINAMICS G, the configuration specifies which bits of the control word
are used and which data is transmitted to the SIMATIC S7-300/400F.
The safety-related communication is also transferred cyclically.
In the SIMATIC S7-300/400F the required functions are activated by selecting
an additional PROFIsafe message frame.
The configuration of the safety functions to be used specifies in the SINAMICS
G whether and which PROFIsafe message frame is expected by the SIMATIC
S7-300/400F.

Acyclic data exchange (parameter access)

The original PROFIBUS specification (now referred to as PROFIBUS DPV0) only
allowed exchange of cyclic data.
To be able to transfer parameters, message frame types were defined where four
words are provided for a parameter (PIV) transfer. Since these four words, like the
process data (PZD), are always transmitted, a permanent communication load is
produced even though the parameters themselves are generally only rarely
transferred.
PROFIBUS DPV1 provides the option to use acyclic data exchange, used only
when required, in addition to cyclic data exchange.
The acyclical data exchange which is only used if necessary. This makes it
possible to transfer the parameter area acyclically on demand, without creating a
permanent communication load. The acyclic transfer takes clearly longer than the
cyclic transfer of the process data.
In the example, acyclic data exchange is used to access the parameters.
In the SIMATIC S7-300/400F, parameter jobs are sent to the SINAMICS G by
writing data record 47, and the response of the SINAMICS G is read in by
reading data record 47.
No particular action is required on the SINAMICS G.
Note When using a CP341-5, the parameters of the SINAMICS G cannot be accessed
and no fail-safe communication can be transferred.
SINAMICS G120C at S7-300/400F-DP
Beitrags-ID: 60441457, V2.2,
chapter 7.4.1
11/2014
of the SINAMICS G120C operating
8