Restrictions In Using Synchronous Unit Operation - Omron CJ2 CPU UNIT SOFTWARE User Manual

10 CPU Unit Functions

10-8-5 Restrictions in Using Synchronous Unit Operation

Restrictions on the Synchronous Operation Cycle Time
Set the synchronous operation cycle time so that the following two conditions are met.
1. The synchronous processing time must be less than the synchronous operation cycle time.
* Generally speaking, set the synchronous operation cycle time to 1.5 times the synchronous processing time or
higher.
2. The internal processing time of a Synchronous Unit must be less than the synchronous cycle time.
1. Synchronous Processing Time
The synchronous processing time is the total of the following two times.
(1) The time from when the synchronous signal is generated until execution of the syn-
chronous interrupt task has been completed (i.e., the total of the following: synchro-
nous output data refresh time, normal processing time, synchronous input data
refresh time, and the synchronous input task execution time)
(2) The time required to executed any I/O interrupt tasks or external interrupt tasks that
occur during the processing described in (1), above. (The maximum and present val-
ues of the synchronous processing time can be monitored in the Synchronous Oper-
ation Status Dialog Box of the CX-Programmer.)
2. Internal Processing Time of a Synchronous Unit
The internal processing time of a CJ1W-NC@@4 Position Control Unit is 1 ms, so the synchronous
operation cycle time must be at least 1 ms.
3. Failure to Meet the Above Conditions
Synchronous Operation Cycle Time Is Shorter Than the Synchronous Processing Time
The next synchronous operation cycle will be entered during execution of the synchronous interrupt
task, and I/O interrupt task, or external interrupt task. This will cause a synchronous processing time
over error in the CPU Unit. The synchronous interrupt task and synchronous data refresh will not be
executed once in that synchronous operation cycle.
Synchronous Operation Cycle Time Is Shorter Than the Internal Processing Time of the
Synchronous Unit
The next synchronous operation cycle will be entered before the Synchronous Unit completes inter-
nal process. This will cause a synchronous processing time over error in the Synchronous Unit. Pro-
cessing will continue in the Synchronous Unit (e.g., axis operations will continue for a Position
Control Unit).
Increases in the Normal Cycle Time
When synchronous unit operation is used, the normal cycle time will be increased by the following
times.
(1) The execution time for the synchronous interrupt time (This is the same as for normal
scheduled interrupts.)
(2) The synchronous input and output data refresh times
10-92 CJ2 CPU Unit Software User's Manual