Omron C200HW-PRM21 Operation Manuals page 114

Sample program to determine PROFIBUS-DP cycle time.
After determining the cycle time of the PROFIBUS-DP system, it is possible to establish the optimal data
exchange method using the actual PLC application program.
98
Activate the I/O data
exchange.
Check if the unit is in Operate
state (102.15 ON) and all
slaves are in data exchange
mode (102.03 OFF), then:
If new input data is received
in the last I/O refresh (102.00
ON), the PLC scan time (set
in DM0000) will be decreased
by the minimum step size of
0.1 ms.
The scan time cannot be
decreased below 0.0 ms
If no new data has been
received during I/O refresh
(102.00 OFF), the previous
PROFIBUS cycle took longer
than the PLC cycle. The PLC
scan time is increased by 0.2
ms. It is essential that rate of
increase is larger than the
rate of decrease, in order to
stabilise the process of
approximation.
The value in DM0000 is set
as scan time for the next PLC
cycle.