3
Programming Concepts Section 1-1
One feature of the cyclic tasks is that they can be enabled (executable status)
and disabled (standby status) by the task control instructions. This means that
several program components can be assembled as a task, and that only spe-
cific programs (tasks) can then be executed as needed for the current product
model or process being performed (program step switching). Therefore perfor-
mance (cycle time) is greatly improved because only required programs will
be executed as needed.
A task that has been executed will be executed in subsequent cycles, and a
task that is on standby will remain on standby in subsequent cycles unless it is
executed again from another task.
Note Unlike earlier programs that can be compared to reading a scroll, tasks can
be compared to reading through a series of individual cards.
• All cards are read in a preset sequence starting from the lowest number.
• All cards are designated as either active or inactive, and cards that are
inactive will be skipped. (Cards are activated or deactivated by task con-
trol instructions.)
• A card that is activated will remain activated and will be read in subse-
quent sequences. A card that is deactivated will remain deactivated and
will be skipped until it is reactivated by another card.
I/O refreshing
Allocation
CP1H
I/O refreshing
Earlier system
One continuous
subprogram
Task 3
Task 2
Task 1
Tasks can be put into non-
executing (standby) status.
To Next Page
Loading...
