Omron SYSMAC CS Series Operation Manual page 95

Difference between I/O Refreshing in Customizable
Preventing the Customizable Counter Unit from Missing Consecutive I/O Refreshes
1,2,3...
■
When the Cycle Time of the CPU Unit Can Be Changed
Use the constant cycle time function on the CPU Unit to change the cycle time
of the Unit so it is longer than the sum total of the cycle time for the Customiz-
able Counter Unit and the I/O refresh time of the CPU Unit as expressed by
the formula below.
CPU Unit Customizable
>
cycle Counter Unit
cycle time
■ When the Cycle Time of the CPU Unit Cannot Be Changed
If the cycle time for the CPU Unit cannot be changed because of the effect the
change would have on system performance, then perform steps (1) and (2)
below.
1. Use the PLC Setup in the CPU Unit to disable cyclic refresh for the Special
I/O Unit number corresponding to the Customizable Counter Unit.
2. Use a timer or some other means to execute the IORF instruction in the
ladder program in the CPU Unit at a time interval longer than the cycle time
of the Customizable Counter Unit. Be sure to refresh the I/O in shared
memory in the Customizable Counter Unit as needed.
Note For customers using -V1 lot No. 0302 or later products
Use the I/O Refresh Monitor Error Flag (CIO 23513 in the Customiz-
able Counter Unit, bit 13 word n+5 in the CPU Unit) to verify whether
the Customizable Counter Unit has performed consecutive I/O re-
freshes.
I/O Refresh Monitor Error Flag:
This flag turns ON when the number of consecutive I/O refreshes missed in
shared memory by I/O refreshing the Customizable Counter Unit exceeds a
preset monitored count.
The monitored count can be set to any number in bits 08 to 15 in word m+6 in
the initial setting area (word m to m+9) in the DM Area words allocated to the
Counter Unit in the CPU Unit (00: 10 times (default), 01 to FF: (1 to 255)).
If a non-fatal error (FAL 99) occurs with the following ladder program for exam-
ple, check the cycle times and change one or the other so the cycle time of
the CPU Unit is longer than the sum total of the cycle time of the Customiz-
able Counter Unit and the I/O refresh time of the CPU Unit.
Example: Customizable Counter Unit
235.13
I/O Refresh Monitor Error Flag
This flag turns OFF when the Customizable Counter Unit enters RUN mode,
and turns ON as soon as the number of missed I/O refreshes exceeds the
preset monitored count.
CPU Unit I/O refresh
+
time
Customizable Counter Unit
CIO 235 bit 13 bit 13 in word n+5
FAL 99
Section 4-5
CPU Unit
75