3.1 Basic Functionality
Execution Scheduling
3-31
3
CPU Unit Functionality
Execution Scheduling
This section describes the execution order of drawings.
Controlling the Execution of Drawings
Drawings are executed based on their priorities, as shown in the following figure.
*1. DWG.A drawings are executed immediately after the power supply is turned ON.
*2. When an interrupt signal is input, execution of the DWG.I drawing is given priority even if execution of a DWG.H or
DWG.L drawing is currently in progress.
Note: The parent drawing of each drawing is automatically called and executed by the system.
Scheduling the Execution of High-speed and Low-speed Scan Pro-
cess Drawings
High-speed scan process drawings (DWG.H) and low-speed scan process drawings (DWG.L) cannot be
executed at the same time. DWG.L drawings are executed during the idle time of DWG.H drawings.
The period during which DWG.H drawings are executed is called the high-speed scan time. The period
during which DWG.L drawings are executed is called the low-speed scan time.
* Background processing is used to execute internal system processing, such as communications processing.
Refer to the following section for the setting procedure for the high-speed and low-speed scans.
Setting the High-speed and Low-speed Scan Times (page 3-34)
Power ON
DWG.A
(Startup Drawings)
Interrupt signal
DWG.I
(interrupt drawing)
Execution is continued
from the point before
the interrupt.
Every low-speed scan
Batch output
Batch input
DWG.L (low-speed
scan process drawing)
Every high-speed scan
Batch output
Batch input
DWG.H (high-speed
scan process drawing)
*1
*2
Low-speed scan time
High-speed
scan time
High-speed
scan time
High-speed
scan time
High-speed
scan time
DWG.H
(high-speed
scan process
drawing)
DWG.L
(low-speed
scan process
drawing)
Background
processing*
: Actual processing time during the scan