Lenze E94AYCER - Manual (Page 73)

Lenze · E94AYCER communication module (PROFINET®) · Communication Manual · DMS 9.0 EN · 12/2013 · TD17
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9 Parameter data transfer
9.5 Consistent parameter data
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9.5 Consistent parameter data
In the PROFINET communication system, data is permanently exchanged between the host
(CPU + IO Controller) and the Servo Drive 9400 via the plugged-on communication module. The IO
Controller and the CPU (central processing unit) of the host access a joint memory: The dual port
memory (DPM).
The DPM permits a 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.
In order to avoid such an impermissible state, the parameter data to be transmitted must be marked
as "consistent".
Data communication with consistent data
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 is not reading, 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 an appropriate Configuration of the IO Controller.
Information on the issue can be found in the documentation of your configuring
software.