Equipments (Devices) > SCA06 > Ladder > Logic > Logic Bit

Logical block that revolutions the value of a specific bit in a field.

Ladder Representation

TESTBIT_block

Block Structure

Variable Type	Name	Data Type	Description
VAR_INPUT	Data	BYTE USINT SINT WORD UINT INT DWORD UDINT DINT	Variable whose bit will be tested
	EN	BOOL	Block enabling
	Position	BYTE USINT	Position of the bit that will be changed
VAR_OUTPUT	Q	BOOL	Value of the tested bit

Operation

This block when it has a TRUE value in EN, sends to the output Q the bit value indicated in Position in the Data variable.

When EN has FALSE value, Q also receives FALSE.

NOTE!

It is important to notice that Position is within the range of values of bits corresponding to variable type in Data. For example: if Data is a BYTE, it has 8 bits, and Position must contain a value between 0 and 7.

Block Flowchart

TESTBIT_flowchart

Example in Ladder

TESTBIT_example01

The example above sets the bit value of zero position of AUX, whose initial value is 74 (0100 1010 in binary) to the output Q. Since this bit has value 0, the output is disabled.

TESTBIT_example02

The example above sets the value of the bit of position three of AUX to the output Q. Since this bit has value 1, the output is enabled.

TESTBIT_example03

The example above sets the bit value of position ten of AUX to output Q. Since AUX is a variable of BYTE type, it has only eight bits. Thus, the example above creates a runtime error in the block and therefore the output is disabled.

Example in ST

The example below displays the instructions for applying the example above in the ST language.

VAR

AUX : BYTE := 2#0100_1010;

POS : BYTE := 3;

END_VAR

DO1 := FB_TESTBIT(

EN:=DI1,

Data:=AUX,

Position:=POS);