RESETBIT

Resets a specific bit in a data field.

Ladder Representation

Block Structure

Variable Type	Name	Data Type	Description
VAR_IN_OUT	Data	BYTE USINT SINT WORD UINT INT DWORD UDINT DINT	Variable whose bit is changed.
VAR_INPUT	EN	BOOL	Block enable.
VAR_INPUT	Position	BYTE USINT	Position of the bit to be changed.
VAR_OUTPUT	Done	BOOL	Operation success.

Operation

When EN is TRUE, the block resets the bit indicated by Position in Data and returns Data with the updated value.

When EN is FALSE, Data remains unchanged.

DONE receives the EN value, except when a bit reset error occurs. In that case, DONE receives FALSE.

Position Range

Make sure Position is within the valid bit range for the Data type. For example, BYTE has 8 bits, so Position must be between 0 and 7.

Execution Flowchart

Examples

Ladder Example

Example 1 resets bit position 0 of AUX, whose initial value is 200, or 1100 1000 in binary. Because this bit is already FALSE, the value is not changed.

Example 2 resets bit position 3 of AUX, changing its binary value and decimal representation.

Example 3 resets bit position 9 of AUX. Because AUX is a BYTE variable with only 8 bits, the block generates an execution error and the output is not enabled.

Structured Text Example

The following Structured Text code applies the same logic shown in the Ladder example.

Structured Text

VAR
    AUX : BYTE := 2#1101_0000;
    POS : BYTE := 3;
END_VAR

DO1 := FB_RESETBIT(
EN:=DI1,
Data:=AUX,
Position:=POS);