Cycle Time and Time Section 9-2
196
The time elapse when Step Run will be as follows.
Minimum Cycle Time
Enabling Minimum Cycle Time will set either the calculated value of the virtual
cycle time or the specified Minimum Cycle Time, whichever is greater, as the
virtual cycle time. The calculated value of the virtual cycle time can be moni-
tored in the detailed mode display of the [System Status].
Note
The Minimum Cycle Time process in the virtual cycle time is not a process
where the execution stands by till the cycle time reaches the specified value,
but where the Minimum Cycle Time is set.
Major Error Factors in the Virtual Cycle Time and Actual CS/CJ/CP-series CPU Unit's Cycle Time
Process Item Error factor/Error range
Computing Time Using such a lot of instructions that greatly varies in
instruction processing time depending on their pa-
rameters (e.g. Data Movement instructions) influences
the computing time. For example, a maximum of
322.35 ± 311.15 µs (1 word vs. 1000 words) error will
occur for one Block Transfer instruction execution.
I/O Refresh Time For the Special I/O Unit, CPU Bus Unit, or Inner Board,
using such a Unit that varies in I/O refresh time de-
pending on the Unit's status or settings changes I/O
refresh time. For example, I/O refresh time will be
4.3 ms when the Position Control Unit
(C200HW-NC413) is mounted and 5.5 ms when read-
ing/writing, making an error of 1.2 ms.
Peripheral Servicing time When "Fixed Peripheral Servicing Time" is disabled,
4% of the immediately previous cycle time is serviced
for each event service. When the immediately previous
cycle time is 10 ms, an error of 10 ms × 0.04 × 6 (event
services) = 2.4 ms will occur if the longest time is ser-
viced for all of the event services.
Computer Cycle Time
The computer cycle time is the actual elapsed time of the Ladder Engine
executed on the computer, which is the execution time depending on the
computer's performance. It is different from the cycle time where an actual
PLC operates.
Virtual
Time
Instruction execution time
One step
execute
Wait One step
execute
Wait One step
execute
Wait One step
execute
P
ocess
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