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Chapter 4. Ladder Diagram (LD) Programming
4.5 Control Functions
The control functions limit program execution and change the way the CPU executes the application
program.
Function
Mnemonic
Do I/O
DO_IO
Drum
DRUM
Edge Detectors F_TRIG
R_TRIG
For Loop
FOR_LOOP
EXIT_FOR
END_FOR
Mask I/O
MASK_IO_INTR Mask or unmask an interrupt from an I/O module when using I/O variables. If
Interrupt
Proportional
PID_ISA
Integral
PID_IND
Derivative
Control
Read Switch
SWITCH_POS Reads position of the Run/Stop switch and the mode for which the switch is
Position
Scan Set IO
SCAN_SET_IO Scans the IO of a specified scan set.
Service Request SVC_REQ
Suspend IO
SUS_IO
Suspend or
SUSP_IO_INTR Suspend or resume an I/O interrupt when using I/O variables. If not using I/O
Resume I/O
Interrupt
102
PACSystems* RX7i, RX3i and RSTi-EP CPU Programmer's Reference Manual
Description
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. Repeats the logic between the FOR_LOOP instruction and END_FOR
instruction a specified number of times or until EXIT_FOR is encountered.
not using I/O variables, use
described in Chapter 6.
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.
configured.
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.
SVC_REQ 32: Suspend/Resume I/O Interrupt
variables, use
Chapter 6.
SVC_REQ 17: Mask/Unmask I/O Interrupt
,
, described in
GFK-2950C
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