Description of Operation
Section
3-2
93
3-2-6-4
Operation of the Loop Control Unit when the CPU Unit is in the Output
OFF condition
The Loop Control Unit continues to run even if the Output OFF flag causes
output refreshing of the CPU Unit to stop. Note, however, that in this case
contacts are not output and turn OFF, and the output hold function of the
Analog Output Unit holds analog output to a specific value. For this reason,
the Loop Control Unit only performs internal operations, and does not
perform control on the outside.
3-2-7
Specifying the Operation Cycle
All of the function blocks (for example, all Field Terminals and the Step
Ladder Program block) on the Loop Control Unit are executed cyclically.
Basically*1, all function blocks (including the Step Ladder Program block) are
executed at a default common operation cycle of one second that is set in the
System Common block (Block Model 000). In other words, at the default
setting, the operation cycle of all function blocks is one second, and all
function blocks are executed at every second.
For example, when all function blocks A, B, C and D in the figure below are
executed and the total execution time is less than one second, function block
execution idles until the preset 1-second operation cycle is reached, and
execution is resumed from function block A as the next operation cycle.
Function block B
Function block A
Function block C
Operation cycle
All function blocks
are executed
(cyclically within this
cycle) in one second
as the default.
Function block D
Idling
(standby time)
Note: Idling is performed after
execution of function blocks
to set a constant cycle.
