Rockwell Automation Publication 1756-RM003N-EN-P - October 2011 393
Array (File)/Misc. Instructions (FAL, FSC, COP, CPS, FLL, AVE, SRT, STD, SIZE) Chapter 8
Arithmetic Status Flags: Arithmetic status flags are affected.
Fault Conditions:
Execution:
A major fault will occur if Fault type Fault code
.POS < 0 or .LEN < 0 4 21
Dimension to vary does not exist for the
specified array
420
Condition Relay Ladder Action
Prescan The .EN bit is cleared.
The .DN bit is cleared.
The .ER bit is cleared.
The rung-condition-out is set to false.
Rung-condition-in is true The STD instruction calculates the standard deviation of the specified elements.
Internally, the instruction uses a FAL instruction to calculate the average:
Expression = standard deviation calculation
Mode = ALL
For details on how the FAL instruction executes, see page 351
.
Postscan The rung-condition-out is set to false.
Examine .DN bit.
.DN Bit = 0
.DN Bit = 1
Rung-condition-in is false.
Rung-condition-out is set
to false.
End
.EN bit is cleared.
.ER bit is cleared.
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