Omron CJ Series User Manual

5 Operation
5-36
CJ-series PROFIBUS Master Unit Operation Manual for NJ-series CPU Unit (W509)
PROFIBUS DP I/O data exchange cycle > CPU cyclic refresh results in the following I/O transfer
characteristics.
• Not all output data is guaranteed to be transmitted over the PROFIBUS network (referring to
the figure above: Output data marked with “O” is overwritten by “O+1” and therefore lost).
• Input data is always sent to the CPU.
Note 1 CPU cyclic refresh times may vary, depending on the execution of the user program. If vari-
ation is too large, this may result in I/O data being lost.
2 To prevent output data not being transmitted over the PROFIBUS network the PROFIBUS
DP cycle time must made at least two times the CPU cyclic refresh time. This can be
accomplished by changing the Target Token Rotation time in the Master DTM Configura-
tion User Interface (see section 5-4-2 Setting the Bus Parameters).
 PROFIBUS DP Cycle < CPU Cyclic Refresh
The figure below shows the effects of the cyclic refresh rules for the case in which the PROFIBUS
DP I/O data exchange cycle < CPU cyclic refresh
CPU Cycle
PROFIBUS Cycle
Cycle n
CIO Refresh
Output data refresh
O O+1 O+2 O+4
Input data refresh
I I+1
End of PROFIBUS DP cycle End of PROFIBUS DP cycle
Cycle n+1 Cycle n+2
I+2
O+3
End of PROFIBUS DP cycle
Unit requests
cyclic refresh
Unit requests
cyclic refresh
Unit requests
cyclic refresh
Unit requests
cyclic refresh
Unit requests
cyclic refresh
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Omron CJ Series Specifications

General

Brand	Omron
Model	CJ Series
Category	Controller
Language	English