Lenze E84AYCER - Manual (Page 64)

E84AYCER communication manual (PROFINET)
Parameter data transfer
Consistent parameter data
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EDS84AYCER EN 2.0 - 11/2010
9.5 Consistent parameter data
In the PROFINET communication system, data are permanently exchanged between the
host (CPU + IO controller) and the standard device via the plugged-on IO device interface
module. The IO controller and the CPU (central processing unit) of the host access a joint
memory: the dual port memory (DPM).
 The DPM allows data exchange in both directions (write/read):
It could happen that a slower IO controller writing would be overtaken by a faster CPU
reading within a cycle time without any further data organisation.
To avoid such an impermissible state, the parameter data to be transmitted must be
marked as "consistent".
Data communication with consistency
With consistency, either "reading" or "writing" is possible when the IO controller and the
CPU simultaneously access the memory:
 The IO controller transfers data only as a complete data set.
 The CPU can only access completely updated data sets.
 The IO controller cannot read or write data as long as the CPU accesses consistent data.
The result becomes clear from the example below:
1. As the IO controller can only write when the CPU does not read, the IO controller has to
wait until the data are completely read by the CPU.
2. The IO controller only writes a complete data set into the DPM.
Configuring consistent data
Central processing unit
(CPU)
Dual port memory
(DPM)
IO controller
CPU wants to read. IO controller wants to write at the same
time.
Central processing unit
(CPU)
Dual port memory
(DPM)
IO controller

Note!
Consistency is achieved by a suitable IO controller configuration.
Please refer to the corresponding documentation of your configuring software.