Description of Operation
Section
3-2
106
3-2-10-4
Automatic operation cycle switching function
When the load rate exceeds 100%, all function blocks within that group are
executed even if the preset operation cycle is exceeded. In the figure below,
function block F is executed even though the preset operation cycle is
exceeded. (Note, however, that an error will occur in PID and other
operations.)
When the load rate exceeds 70% continuously for ten times, the operation
cycle is automatically switched to the next longer cycle. (In other words,
ITEM004 of that function block is automatically changed to an updated
operation cycle.) When the operation cycle is automatically switched, the
state of the Operation Cycle Automatic Switching Generator flag of each of
ITEMs ITEM053, ITEM056, ITEM059, ITEM062, ITEM065 and ITEM065 of
the System Common block (Block Model 000) changes from 0 to 1 and is
latched. Once the state of the Operation Cycle Automatic Switching
Generator flag turns 1, it will not return to 0 unless the corresponding ITEM of
the System Common block (Block Model 000) is manually reset on CX-
Process Tool. Also, once the state of the Operation Cycle Automatic
Switching Generator flag turns 1, it will remain 1 even if a longer operation
cycle is automatically switched to.
Note
When the load rate of the 2-second operation cycle exceeds 70%
continuously for ten times, the state of the Operation Cycle Automatic
Switching Generator flag turns 1, and running of all function blocks is
automatically stopped. If this happens, add on another Loop Control Unit, and
distribute processing between the Units.
The Operation Cycle Automatic Switching Generator flag can be monitored
using the Monitor run status screen of CX-Process Tool. Select [Operation]-
[Monitor run status] from the [Execute] menu.
3-2-11 External I/O Refresh Cycle on the Overall System
The Loop Control Unit exchanges field I/O values (analog input values,
analog output values, contact inputs and contact outputs) with external Units
by the following method.
1. The Analog Input/Output Unit or the Basic I/O Unit refresh the I/O
memory on the CPU Unit.
2. The Loop Control Unit exchanges data allocated to I/O memory on the
CPU Unit according to the operation cycle of each function block.