L9_SUB: Subtraction

Naming

Name in LL984 Editor	Function Block Name
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Function Description

The L9_SUB procedure performs subtraction of unsigned VALUE1 minus unsigned VALUE2, and then posts the RESULT in a memory word.

The subtraction operation begins when the input to the ENABLE pin is turned ON.

L9_SUB can activate 1 of 3 outputs. The state of the outputs indicates the relationship between VALUE1 and VALUE2. The GRT output turns ON if VALUE1 > VALUE2. The EQT output turns ON if VALUE1 = VALUE2. The LESSTH output turns ON if VALUE1 < VALUE2.

Formula

RESULT = VALUE1 − VALUE2

Representation

Parameters

Input Pin	Name	Data Type	Address Range	Meaning
Top	ENABLE	BOOL	–	OFF to ON initiates the operation.

Node	Node Type	Name	Data Type	Address Range	Meaning
Top	IN	VALUE1	UINT	%IW, %MW	The minuend (the value subtracted from). Can be displayed as an integer constant, or can be stored in a variable located in a %IW input word, a %MW memory word or an unlocated word. Valid range: 0 to 65,535.
Middle	IN	VALUE2	UINT	%IW, %MW	The subtrahend (the subtracted value). Can be displayed as an integer constant, or can be stored in a variable located in a %IW input word, a %MW memory word or an unlocated word. Valid range: 0 to 65,535.
Bottom	IN/OUT	RESULT	UINT	%MW	The difference of 16-bit subtraction. Note that, if VALUE2 > VALUE1, the RESULT will be stored as a positive value For example, if VALUE1 = 6 and VALUE2 = 7, RESULT = 1 and LESSTH turns ON. The variable tied to this pin must be stored in a %MW memory word or an unlocated UINT word.

Output Pin	Name	Data Type	Address Range	Meaning
Top	GRT	BOOL	–	ON indicates the VALUE1 > VALUE2.
Middle	EQT	BOOL	–	ON indicates the VALUE1 = VALUE2.
Bottom	LESSTH	BOOL	–	ON indicates the VALUE1 < VALUE2.