Logic Blocks; 2Oo3 (2 Out Of 3 Voting); And - Allen-Bradley ProcessLogix 1757 Series Reference Manual

Function blocks
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3-16
Functional Blocks

Logic Blocks

2OO3 (2 out of 3 voting)

Description
2-out-of-3 Voting block – outputs (DISCREP and MAJ) are determined as follows:
DISCREP = NOT (IN [1] = IN [2] = IN [3]) for duration >= DELAY
MAJ = value held by the majority of the inputs.
Function
Sets the output (DISCREP) to ON if NOT all inputs agree for a specified time duration (DELAY); otherwise, it is set to
OFF.
Inputs
IN [1..3] = Boolean values
Outputs
DISCREP & MAJ = Boolean values
Parameters
DELAYTIME
DISCREP

AND

Description
Provides an up to 8-input AND algorithm, meaning that it performs the Boolean operation of conjunction. Each input
,
(IN [1]
IN [2], ..., IN [8]) has the capability of being optionally inverted, if required.
Function
Turns the Boolean value output (OUT) ON only when all inputs (IN [1]
• If all inputs (IN [1..8]) are ON, then: OUT = ON.
• If any input (IN [x]) is OFF, then: OUT = OFF.
If input is inverted, then:
• Actual_IN [x] = NOT (IN [x])
• Else, Actual_IN [x] = IN [x]
Where x equals any valid input.
Truth Table
IN [1]
OFF
OFF
ON
ON
Inputs
IN [1..8] = Boolean value
Outputs
OUT = Boolean value controlled by the status of the input signals.
Parameters
IN [1..8]
INPTINVSTS [1..8]
Publication 1757-RM810A-EN-P - May 2002
EUDESC
HIALM
IN [2]
OFF
ON
OFF
ON
ORDERINCM
OUT
IN [0..2]
MAJ
,
IN [2], ..., IN [8]) are ON. Therefore:
OUT
OFF
OFF
OFF
ON
ORDERINCM

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