26 REDUNDANT FUNCTION
26.11 Precautions on Programming
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26.11 Precautions on Programming
This section describes the precautions on programming for a redundant system.
Instructions not available in redundant system
This section describes the instructions not available in a redundant system.
Instructions that cause stop errors
Do not use the following instructions when the redundant system is in backup mode. Doing so causes an error when the
operating status of the CPU module is changed from STOP to RUN.
Instructions that need to be executed again in a new control system
For an instruction that requires several scans for completing the processing, the instruction will be continuously executed
when the system switching is performed during execution of the instruction. When a completion device has been used in an
execution program of the control system, the completion device will not turn on even though the instruction is completed after
the system switching from the control system to the standby system. However, the completion device will turn on after the
system switching from the control system to the standby system and then to the control system again. Note that the
completion status of the completion device is not reflected to the tracking device. When the system switching is performed
during execution of an instruction, execute the instruction again as required.
For some instructions, an error will occur if an instruction is executed during execution of the same instruction. For the
operation for each instruction that is executed again during execution of the same instruction, refer to the following.
MELSEC iQ-R Programming Manual (CPU Module Instructions, Standard Functions/Function Blocks)
MELSEC iQ-R Programming Manual (Module Dedicated Instructions)
Classification Instruction symbol
Special counter instructions Counting up or down the current value (1-phase input) UDCNT1
Counting up or down the current value (2-phase input) UDCNT2
Special timer instructions Teaching timer TTMR
Special function timer STMR
Shortcut control instruction Rotary table shortest direction control ROTC
Ramp signal instruction Ramp signal RAMPQ
Pulse related instructions Measuring the density of pulses SPD
Outputting pulses at regular intervals PLSY
Performing the pulse width modulation PWM
Matrix input instruction Matrix input MTR
Multiple CPU dedicated instructions Reading device data from another CPU module D.DDRD
DP.DDRD
M.DDRD
MP.DDRD
Writing device data to another CPU module D.DDWR
DP.DDWR
M.DDWR
MP.DDWR
Classification Instruction symbol
Data processing instructions SORTD(_U), DSORTD(_U)
Reading/writing data instructions SP.DEVST, SP.FREAD, SP.FWRITE
Open/close processing instructions SP.SOCOPEN, SP.SOCCLOSE
Socket communications instructions SP.SOCRCV, S.SOCRCVS, SP.SOCSND, SP.SOCCINF, SP.SOCCSET,
SP.SOCRMODE, S(P).SOCRDATA
SLMP frame send instruction SP.SLMPSND
File transfer function instruction SP.FTPPUT, SP.FTPGET
Module dedicated instructions Instructions that require several scans for completing processing
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