Rockwell Automation Publication 1756-RM003N-EN-P - October 2011 269
Compute/Math Instructions (CPT, ADD, SUB, MUL, DIV, MOD, SQR, SQRT, NEG, ABS) Chapter 6
Subtract (SUB)
The SUB instruction subtracts Source B from Source A and places the result in
the Destination.
Operands:
Relay Ladder
Structured Text
Use the minus sign “−” as an operator in an expression. This expression subtracts
sourceB from sourceA and stores the result in dest.
See Structured Text Programming
for information on the syntax of expressions
within structured text.
Function Block
Operand Type Format Description
Source A SINT
INT
DINT
REAL
Immediate Tag Value from which to subtract Source B
A SINT or INT tag converts to a DINT value by sign-extension.
Source B SINT
INT
DINT
REAL
Immediate Tag Value to subtract from Source A
A SINT or INT tag converts to a DINT value by sign-extension.
Destination SINT
INT
DINT
REAL
Tag Tag to store the result
Operand Type Format Description
SUB tag FBD_MATH structure SUB structure
dest := sourceA - sourceB;
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