Chapter 4. Ladder Diagram (LD) Programming
102 PACSystems* RX7i, RX3i and RSTi-EP CPU Programmer's Reference Manual GFK-2950C
4.5 Control Functions
The control functions limit program execution and change the way the CPU executes the application
program.
For one scan, immediately services a specified range of inputs or outputs. (All
inputs or outputs on a module are serviced if any reference locations on that
module are included in the DO I/O function. Partial I/O module updates are
not performed.) Optionally, a copy of the scanned I/O can be placed in
internal memory, rather than at the real input points.
Provides predefined On/Off patterns to a set of 16 discrete outputs in the
manner of a mechanical drum sequencer.
Detect the changing state of a Boolean signal.
FOR_LOOP
EXIT_FOR
END_FOR
For loop. Repeats the logic between the FOR_LOOP instruction and END_FOR
instruction a specified number of times or until EXIT_FOR is encountered.
Mask or unmask an interrupt from an I/O module when using I/O variables. If
not using I/O variables, use SVC_REQ 17: Mask/Unmask I/O Interrupt,
described in Chapter 6.
Proportional
Integral
Derivative
Control
Provides two PID (Proportional/Integral/Derivative) closed-loop control
algorithms:
Standard ISA PID algorithm (PID_ISA)
Independent term algorithm (PID_IND)
Note: For details, refer to Chapter 7.
Reads position of the Run/Stop switch and the mode for which the switch is
configured.
Scans the IO of a specified scan set.
Requests a special PLC service.
Note: For details, refer to Chapter 6.
Suspends for one sweep all normal I/O updates, except those specified by DO
I/O instructions.
Suspend or
Resume I/O
Interrupt
Suspend or resume an I/O interrupt when using I/O variables. If not using I/O
variables, use SVC_REQ 32: Suspend/Resume I/O Interrupt, described in
Chapter 6.
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