Allen-Bradley LOGIX 5000 Reference Manual page 355

Select_Limit Instructions
Description
The ESEL instruction operates as follows
Condition
SelectorMode = 0 (manual select) or
Override is true, ProgOper is false and
OperSelector is not equal to 0
SelectorMode = 0 (manual select) or
Override is true, ProgOper is true and
ProgSelector is not equal to 0
SelectorMode = 1 (high select) and
Override is false
SelectorMode = 2 (low select) and
Override is false
SelectorMode = 3 (median select) and
Override is false
SelectorMode = 4 (average select) and
Override is false
For SelectorMode 1 through 4, a bad health indication for any of the inputs causes
that bad input to be disregarded in the selection. For example, if SelectorMode = 1
(high select) and if In6 had the highest value but had bad health, then the next
highest input with good health is moved into the output.
For high or low select mode, if two inputs are equal and are high or low, the
instruction outputs the first found input. For median select mode, the median
value always represents a value selected from the available inputs. If more than one
value could be the median, the instruction outputs the first found input.
Switch Between Program Control and Operator Control
The following diagram shows how the ESEL instruction changes between
Program control and Operator control.
(1) You can lock the instruction in Operator control mode by leaving
ProgOperReq true.
Rockwell Automation Publication 1756-RM006K-EN-P - November 2018
Action
Out = In[OperSelector]
SelectedIn = OperSelector
Out = In[ProgSelector]
SelectedIn = ProgSelector
Out = maximum of In[InsUsed]
SelectedIn = index to the maximum input value
Out = minimum of In[InsUsed]
SelectedIn = index to the minimum input value
Out = median of In[InsUsed]
SelectedIn = index to the median input value
Out = average of In[InsUsed]
SelectedIn = 0
Chapter 4
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