Chapter 4. Ladder Diagram (LD) Programming102 PACSystems* RX7i, RX3i and RSTi-EP CPU Programmer's Reference Manual GFK-2950C4.5 Control FunctionsThe control functions limit program execution and change the way the CPU executes the applicationprogram.Function Mnemonic DescriptionDo I/O DO_IO For one scan, immediately services a specified range of inputs or outputs. (Allinputs or outputs on a module are serviced if any reference locations on thatmodule are included in the DO I/O function. Partial I/O module updates arenot performed.) Optionally, a copy of the scanned I/O can be placed ininternal memory, rather than at the real input points.Drum DRUM Provides predefined On/Off patterns to a set of 16 discrete outputs in themanner of a mechanical drum sequencer.Edge Detectors F_TRIGR_TRIGDetect the changing state of a Boolean signal.For Loop FOR_LOOPEXIT_FOREND_FORFor loop. Repeats the logic between the FOR_LOOP instruction and END_FORinstruction a specified number of times or until EXIT_FOR is encountered.Mask I/OInterruptMASK_IO_INTR Mask or unmask an interrupt from an I/O module when using I/O variables. Ifnot using I/O variables, use SVC_REQ 17: Mask/Unmask I/O Interrupt,described in Chapter 6.ProportionalIntegralDerivativeControlPID_ISAPID_INDProvides two PID (Proportional/Integral/Derivative) closed-loop controlalgorithms:Standard ISA PID algorithm (PID_ISA)Independent term algorithm (PID_IND)Note: For details, refer to Chapter 7.Read SwitchPositionSWITCH_POS Reads position of the Run/Stop switch and the mode for which the switch isconfigured.Scan Set IO SCAN_SET_IO Scans the IO of a specified scan set.Service Request SVC_REQ Requests a special PLC service.Note: For details, refer to Chapter 6.Suspend IO SUS_IO Suspends for one sweep all normal I/O updates, except those specified by DOI/O instructions.Suspend orResume I/OInterruptSUSP_IO_INTR Suspend or resume an I/O interrupt when using I/O variables. If not using I/Ovariables, use SVC_REQ 32: Suspend/Resume I/O Interrupt, described inChapter 6.
